UDK: 111:57 FILOZOFIJA I DRUŠTVO XXIV (4), 2013. DOI: 10.2298/FID1304181P Original scientific paper

Slobodan Perović Department of Philosophy University of Belgrade

The Rebirth of the Morphogenetic Field as an Explanatory Tool in Biology

Abstract I discuss two uses of the concept of the morphogenetic field, a tool of the 19 th century biology motivated by particular ontological views of the time, which has been re-emerging and increasingly relevant in explaining microbiological phenomena. I also consider the relation of these uses to the Central Dogma of modern biology as well as Modern Synthesis of Darwini- sm and genetics. An induced morphogenetic field is determined by a physical (e.g., gravitational) field, or it acquires a physical (e.g., visco-elastic) field’s characteristics. Such a morphogenetic field presents only a weak challenge to the Central Dogma of Modern Synthesis by indirectly, albeit severely, con- 181 straining variability at the molecular level. I discuss explanations that intro- duce structural inheritance in ciliate protozoa, as well as the experimental evidence on which these arguments are based. The global cellular morphoge- netic field is a unit of such inheritance. I discuss relevant cases of structural inheritance in ciliates that bring about internal cellular as well as functional changes and point out that DNA is absent in the cortex and that RNA con- trols neither intermediary nor the global level of the field. I go on to argue that utilizing knowledge of known physical fields may advance explanations and understanding of the morphogenetic field in ciliates as the unit of both development and inheritance.

1. Introduction [T]o an evolutionist, the interesting question about …cytoplasmatic localization is not whether such localization is essential for prop- er development, but whether, if the localizations are changed, the result will be an adult which produces eggs with similarly altered localizations. In general, the answer to such questions is no. There are a few well- established exceptions, of which phenomenon of ‘cortical inher- itance’ in ciliates is perhaps the most important. Neo-Darwinists should not be allowed to forget these cases, because they consti- –—–‡–Š‡‘Ž›•‹‰‹Ƥ ƒ–‡š’‡”‹‡–ƒŽ–Š”‡ƒ––‘‘—”˜‹‡™•Ǥȋƒ›ƒ”† Smith 1983, 39)

Judging by recent studies of the so-called structural inheritance in cili- ates and related phenomena of cytoplasmatic inheritance, one might conclude that Neo-Darwinists have reason to be worried. ͱ And these

1 This work was supported by the project “Dynamic Systems in nature and society: ’Š‹Ž‘•‘’Š‹ ƒŽƒ†‡’‹”‹ ƒŽƒ•’‡ –•dzȋ‡˜‹†‡ ‡͛ͣͥ͜͝͠͝ȌƤƒ ‡†„›–Š‡‹‹•–”› SLOBODAN P EROVIĆ THE REBIRTH OF THE MORPHOGENETIC FIELD

cases might be only one instance, albeit the most important one, of the ‘”‡’‡”˜ƒ•‹˜‡”‡•—”‰‡ ‡‘ˆ–Š‡ ‘ ‡’–‘ˆ‘”’Š‘‰‡‡–‹ Ƥ‡Ž†Ǥ

Ž–Š‘—‰Š–Š‡‘”‹‰‹•‘ˆ–Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž† ‘ ‡’–ƒ”‡Ž‹‡†–‘ rather obscure Naturphilosophie and the Romantic understanding of life and science, it was a potent tool in the 19 th century study of mor- phogenesis. While it was initially sidelined in an age of biology predi- cated on Darwinism married to genetics and the microbiological study ‘ˆŠ‡”‡†‹–ƒ”›—‹–•ȋ‹Ǥ‡Ǥǡ–Š‡•‘Ǧ ƒŽŽ‡†‘†‡”›–Š‡•‹•Ȍǡ–Š‡‘”’Š‘ - ‰‡‡–‹ Ƥ‡Ž†Šƒ•„‡‡‹ ”‡ƒ•‹‰Ž›’Žƒ›‹‰ƒ‹†‹•’‡•ƒ„Ž‡”‘Ž‡‹‡š - plaining development, morphogenesis and inheritance. Indeed, some „‹‘Ž‘‰‹•–•ƒ”‰—‡–Šƒ––Š‡‡‡”‰‹‰ ‘ ‡’–‘ˆ‘”’Š‘‰‡‡–‹ Ƥ‡Ž†”‡’ - resents a serious challenge to and a comprehensive alternative for the •‘Ǧ ƒŽŽ‡†‡–”ƒŽ‘‰ƒ‘ˆ‘†‡”„‹‘Ž‘‰›ȋ”ƒ›͜͜͞͝ǡŠƒ’–‡”͠Ǣ ‹Ž - „‡”–ǡ’‹–œƒ†ƒơǡͥͥ͢͝ǡͤ͟͢Ǣ Œ‡Žͥͤ͢͝Ǣ ‘‘†™‹ͥͤ͝͠ȌǤ 182 Š‡ ‘”‡‘ˆ–Š‡‡–”ƒŽ‘‰ƒ‹•–Šƒ––Š‡‰‡‡•ȋȌƒ”‡–Š‡‡š Ž— - sive hereditary units, and that virtually unlimited variations at the mo- lecular level – the result of mutations and recombination – produce traits that become the subject of natural selection, thereby allowing a ™‹†‡”ƒ‰‡‘ˆ’‘–‡–‹ƒŽƒ†ƒ –—ƒŽ‡˜‘Ž—–‹‘ƒ”› Šƒ‰‡•ȋƒ™‹•ͥͤ͝͞ǡ ͥͥ͝͡Ǣƒ›ƒ”†‹–Šͥͤ͟͝ȌǤŠ—•ǡƒ ‘”†‹‰–‘–Š‡ȋ”‡Ƥ‡†Ȍ‡‹•‡ƒ - nian Neo-Darwinist germ-centrism, DNA controls the details of protein synthesis and activity in morphogenetic and developmental processes ȋƒ‡›ͥͤ͝͠Ǣƒ›ƒ”†‹–Šͥͤ͟͝Ǣƒ™‹•ͥͤ͝͞ȌǤ

‘ŽŽ‘™‹‰–Š‡ƒ„‘˜‡Ǧ“—‘–‡†™ƒ”‹‰ˆ”‘ƒ›ƒ”†‹–Š–Šƒ––Š‡ƒ† - herents to the Central Dogma should not overlook the cases of cyto- plasmatic inheritance, I will discuss the extent of the present challenge –‘–Š‡–‡‡–•‘ˆ‘†‡”›–Š‡•‹•–Šƒ–•–‡•ˆ”‘–Š‡•–—†‹‡•„ƒ•‡† ‘–Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž†™Š‹Ž‡‡š’Žƒ‹‹‰–Š‡ƒ–—”‡‘ˆ–Š‡ ‘ ‡’–Ǥ

2. Induced Morphogenetic Fields

Experimentally based studies of morphogenetic and developmental ’”‘ ‡••‡••—‰‰‡•––Šƒ––Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž†‹‰Š–„‡‹†‹•’‡•ƒ„Ž‡ in explaining developmental, embryogenetic and morpohogenetic pro- cesses, as the explanations of such processes introduce the level beyond

of Education, science and technological development of the Republic of Serbia. I would like to thank Jan Sapp, Carlos Sonnenschein and J. Frankel for their helpful comments and fruitful discussions on the topic, a well as the participants of the •‡‹ƒ”ƒ––Š‡ƒ Ž‡” Š‘‘Ž‘ˆ‹‘‡†‹ ƒŽ ‹‡ ‡ƒ–—ˆ–•‹˜‡”•‹–›™Š‡”‡–Š‡ work was presented. THE NOTION AND STRUCTURE OF EXPLANATION IN THE NATURAL AND SOCIAL SCIENCES

the molecular one as provider of genetic information. In arguing this ’‘‹–ǡ ‘‘†™‹ȋͥͤ͝͠ǡͥ͞͝Ȍƒ’’‡ƒŽ•–‘Dz–Š‡‡’‹”‹ ƒŽ‡˜‹†‡ ‡–Šƒ–‰‡‡ products do not generate form.” Some even assert that the rebirth of –Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž†‹•Dz•–ƒ”–‹‰–‘ƒ‡‰‘‘†‘‘—šǯ•’”‘’Š‡ - cy” that “phylogenetic developmental mechanics would determine how Šƒ‰‡•‹‡„”›‘‹ †‡˜‡Ž‘’‡– ƒ—•‡‡˜‘Ž—–‹‘ƒ”› Šƒ‰‡Ǥdzȋ ‹Ž - „‡”–ǡ’‹–œǡƒ†ƒơͥͥ͢͝ǡͤ͟͢Ȍ

Thus, in the case of Drosophila  ‡„”›‘• ȋ ‘‘†™‹ ͥͤ͝͠ǡ ͣ͞͞Ǣ ‘Ž† - schmidt 1935) gene activity should be treated simply as stimuli which ƒ”‡‘–‘”‡”‡Ƥ‡†–Šƒ‡š–‡”ƒŽ”ƒ†‘•–‹—Ž‹Ǣ–Š‡•‡•–‹—Ž‹–”‹‰‰‡” a response by means of an intrinsic morphogenetic mechanism. Thus, –Š‡‰‡‡•†‘‘–‹ƪ—‡ ‡‡„”›‘‰‡‡•‹•‹ƒƒ‡”ƒƒŽ‘‰‘—•–‘–Š‡ computer program that determines each stage. If the embryos are ex- ’‘•‡†ˆ‘”„”‹‡ˆ’‡”‹‘†•–‘‡š–‡”ƒŽ‘Ǧ•’‡ ‹Ƥ •–‹—Ž‹ȋ‡–Š‡”ǡ‡Ž‡˜ƒ–‡† 183 temperature, X-rays, etc.), the morphology of the adult will be altered in •’‡ ‹Ƥ  ™ƒ›• and genetic mutations will alter it in the same ways ȋ–‡–ͥͤ͝͞Ǣ ‘Ž†• Š‹†–ͥ͟͝͡ȌǤŠ‡ˆƒ ––Šƒ–”ƒ†‘‹ƪ—‡ ‡•ƒ†‰‡ - ‡–‹ —–ƒ–‹‘•„‘–Š’”‘†— ‡–Š‡•ƒ‡•’‡ ‹Ƥ ƒŽ–‡”ƒ–‹‘••—’’‘•‡†Ž› indicates the limited response repertoire of a highly structured internal morphogenetic mechanism. The stability of this mechanism is the ba- •‹•‘ˆ–Š‡ȋ•–ƒ„‹Ž‹–›‘ˆȌ‘”’Š‘‰‡‡–‹ ’”‘ ‡••‡•ǡ–Š‡”‡„›•‹†‡Ž‹‹‰‰‡ - netic dominance beyond the stage of protein formation.

The previous case is a particularly illustrative example of the so-called Š‘‡‘–‹  —–ƒ–‹‘• ȋ ‹Ž„‡”–ǡ ’‹–œ ƒ† ƒơ ͥͥ͢͝ǡ ͟͢͟Ǧ͠Ǣ ‘‘†™‹ ͥͤ͝͠ǡ͢͞͞ȌǤ ‰‡‡”ƒŽǡ•— Š—–ƒ–‹‘•”‡•—Ž–‹˜ƒ”‹‘—• Šƒ‰‡•‘ˆ–Š‡ structure of appendages. Such mutations in Drosophila can, for exam- ple, result in the growth of a leg on a segment of a body to which a dif- ˆ‡”‡–ƒ’’‡†ƒ‰‡ȋƒ–‡ƒȌ‘”ƒŽŽ›„‡Ž‘‰•Ǥ‘”‡‘˜‡”ǡ ‡”–ƒ‹‰‡‡ sequences, namely the homeotic genes responsible for the formation of –Š‡ƒ’’‡†ƒ‰‡••–”— –—”‡ȋƒ†™Š‹ Š—–ƒ–‡‹Š‘‡‘–‹ —–ƒ–‹‘•Ȍǡ †‘‘–†‹ơ‡”ƒ ”‘•••’‡ ‹‡• ȋ ‹Ž„‡”–ǡ’‹–œƒ†ƒơͥͥ͢͝ȌǤ ‘”‹•–ƒ ‡ǡ the order of homeotic genes in chromosomes turns out to be identical ‹˜‡”–‡„”ƒ–‡•ƒ†–Š‡ƪ›ȋ ‹‹•ƒ†”—Žƒ—ˆͥͥ͝͞Ǣ”—Žƒ—ˆͥͥ͟͝Ǣ ƒ Š‹ŽŽ‡”‡–ǤƒŽǤͥͥ͝͠ȌǤŽ•‘ǡ‹•‘‡ ƒ•‡•ǡ the individual homeotic gene ‡š’”‡••‹‘‹•‹†‡–‹ ƒŽ‹†‹ơ‡”‡–•’‡ ‹‡• ȋ‡Ǥ‰Ǥǡ‹Š—ƒ•ƒ†”‘•‘’Š - ‹ŽƒȌȋ ‹‹•‡–ƒŽǤͥͥ͜͝ǢƒŽ‹ ‹‡–ƒŽǤͥͥ͝͞ȌǤ

Although homology is a complex issue that is related to the mechanism of natural selection and the concept of biological function in various SLOBODAN P EROVIĆ THE REBIRTH OF THE MORPHOGENETIC FIELD

™ƒ›•ȋ ”‹ƥ–Š•ͣ͜͜͞Ȍǡ–Š‡‡š‹•–‡ ‡‘ˆŠ‘‡‘–‹ ‰‡‡•ƒ†–Š‡‹”‡š’”‡• - sion demonstrates the striking similarities of embryonic development across phyla. The question is – what exactly can we conclude from this?

Taking the Central Dogma point of view, one could argue that embry- ‘‰‡‡•‹•ƒ†‘”’Š‘‰‡‡•‹•‹†‹ơ‡”‡–’Š›Žƒ•‹’Ž›‡ ‘—–‡”•‹ - ilar “problems” and “obstacles” and thus result in similar solutions. This explains the similarity of the genetic sequence responsible for the similar structural changes across phyla, as well as the appearance of genes as mere stimuli in the face of the stability of morphogenetic processes.

—–ˆ‘ —•‹‰‘–Š‡•‡Dz’”‘„Ž‡•dzƒ†Dz‘„•–ƒ Ž‡•dzȋ‹Ǥ‡Ǥǡ ‘•–”ƒ‹–•ȌŠƒ• non-trivial consequences for the understanding of morphogenetic phe- nomena from the gene-centric point of view. 184 From the gene-centric point of view “these constraints are historical and contingent in nature, arising from the existing pattern of develop- ‡–dzȋƒ›ƒ”†‹–Šͥͤ͝͠ǡ͟͠ȌǤ‡––Š‡†‘ƒ‹‘ˆ–Š‡•‡ ‘•–”ƒ‹–•‹• •—”’”‹•‹‰Ž›ƒ””‘™ǡ–Š—•ƒ‹‰‹–’‘••‹„Ž‡–‘†‡Ƥ‡–Š‡ƒ•ƒ ‘ - ‘—†‡”Ž›‹‰•–”— –—”‡ƒ ”‘••’Š›ŽƒǤ—– Žƒ‹–Šƒ–•— ŠƒDzƒŽ–‡” - native to [the] view [of contingent constraints] would be that there are absolute laws of form, not historically contingent, determining what ‹†•‘ˆ‘”‰ƒ‹•• ƒƒ† ƒ‘–‡š‹•–dzȋƒ›ƒ”†‹–Šǡ‹„‹†ǤȌƒ› be incorrect: instead of looking for such independent “absolute laws,” ‘‡ ‘—Ž†ƒ ‘—–ˆ‘”–Š‡ƒ””‘™•‡–‘ˆ ‘•–”ƒ‹–•„›†‡Ƥ‹‰–Š‡‘” - ’Š‘‰‡‡–‹ Ƥ‡Ž† ‹–‡”•‘ˆ–Š‡™‡ŽŽǦ‘™’Š›•‹ ƒŽƤ‡Ž†• . Such an ap- proach raises the question of the interaction of such a morphogenetic Ƥ‡Ž†ȋ‹Ǥ‡Ǥǡ–Š‡ ‘•–”ƒ‹‹‰‡ Šƒ‹•Ȍ™‹–Š–Š‡‰‡‡•Ǥ

The morphogenetic processes are embedded in particular physical ‘–‡š–•ǡ ‹†‡–‹ ƒŽƒ ”‘••’Š›ŽƒǤ ‘”‡’”‡ ‹•‡Ž›ǡ–Š‡›ƒ”‡ ‘•–”ƒ‹‡† „›‘™’Š›•‹ ƒŽŽƒ™•ǤŠ—•ǡ–Š‡Ƥ‡Ž†ǦŽ‹‡’”‘’‡”–‹‡•‘ˆ–Š‡‘”‰ƒ‹• - ƒŽˆ‘”ƒ–‹˜‡’”‘ ‡••‡•ȋ‡Ǥ‰Ǥǡ–Š‡‹”—‹ˆ‘”‹–›ƒ†•–ƒ„‹Ž‹–›Ȍ ‘—Ž† be induced in the organisms „›™‡ŽŽǦ‘™‘™’Š›•‹ ƒŽƤ‡Ž†•ǤŠ—•ǡ –Š‡‰”ƒ˜‹–ƒ–‹‘ƒŽƤ‡Ž†ƒ›‹†— ‡–Š‡•–ƒ‰‡•ƒ†‡˜‡–Š‡†‡–ƒ‹Ž•‘ˆ–Š‡ ‘”’Š‘‰‡‡–‹ ’”‘ ‡••‡• ȋ ‘‘†™‹ ͥͤ͝͠ȌǤŽ–‡”ƒ–‹˜‡Ž› ȋƒ†–Š‹•ƒŽ - ternative is physically and formally more tractable), the morphogenet- ‹ Ƥ‡Ž† ‘—Ž†„‡ƒƤ‡Ž†™‹–Š–Š‡‹†— ‡†’”‘’‡”–‹‡•‘ˆ–Š‡˜‹• ‘Ǧ‡Žƒ•–‹  Ƥ‡Ž†ǡ™Š‡”‡„›–Š‡Žƒ™• ‘ ‡”‹‰–Š‡•Šƒ’‹‰‘ˆ–Š‡‘”‰ƒ‹•ƒ”‡ƒ - ‘—–‡†ˆ‘”„›–Š‡”‡‰—Žƒ”Žƒ™•‘ˆ–Š‡˜‹• ‘Ǧ‡Žƒ•–‹ Ƥ‡Ž†ȋ”ƒ†–•ƒ† ‘–ƒˆ—”‘ͥͥͣ͝Ǣ”ƒ†–•ƒ†”ƒ‹‘”ͥͥ͜͝Ǣ ‘‘†™‹ƒ†”ƒ‹‘”ͥͤ͝͡ȌǤ THE NOTION AND STRUCTURE OF EXPLANATION IN THE NATURAL AND SOCIAL SCIENCES

‡–‡˜‡‹ˆ–Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž††‡–‡”‹‡•Ž‘ ƒŽ‹œƒ–‹‘•‹–Š‡ › - toplasm, and even if it regulates the morphogenetic and developmental ’”‘ ‡••‡•„›•‡˜‡”‡Ž› ‘•–”ƒ‹‹‰–Š‡ˆ‘”ƒ–‹‘‘ˆ–Š‡’”‘–‡‹•ȋ‹Ǥ‡Ǥǡ‹ˆ †‡˜‡Ž‘’‡–‹•†‡Ƥ‡†ƒ•ƒ’ƒ”–‹ —Žƒ”•–ƒ„‹Ž‹œƒ–‹‘‘ˆ–Š‡Ƥ‡Ž†‡“—ƒ - –‹‘•Ȍǡ–Š‡“—‡•–‹‘”‡ƒ‹•ǣƒ”‡–Š‡ Šƒ‰‡•‹– ƒ ƒ—•‡‹Š‡”‹–‡†ȋ„› it)? Nothing in the arguments we have discussed suggests that the posi- tive answer is correct. Nor is it clear whether, due to its very limited var- ‹ƒ„‹Ž‹–›ȋ–Š‡†‹•–”‹„—–‹‘‘ˆ–Š‡ ‘†‹–‹‘‘ˆ–Š‡’Š›•‹ ƒŽƤ‡Ž†Ȃ‰”ƒ˜‹ - tational or visco-elastic – on which it depends remains unchanged over –‹‡Ȍ–Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž† ƒƒ••‹‹Žƒ–‡ƒ›•‹‰‹Ƥ ƒ– Šƒ‰‡•Ǥ

To claim that the DNA-program paradigm is challenged by the neces- •‹–›‘ˆ‹–”‘†— ‹‰–Š‡‹†— ‡†‘”’Š‘‰‡‡–‹ Ƥ‡Ž†ȋƒ• ‘‘†™‹†‘‡•Ȍ is to attack too broad a claim. The proponent of the Central Dogma can respond by saying that while the unfolding of the DNA-based pro- 185 ‰”ƒƒ›‹†‡‡†„‡‹ƪ—‡ ‡†„›–Š‡†‡˜‡Ž‘’‡–ƒŽ ‘•–”ƒ‹–•ǡDzȑ–Ȓ here is … nothing ‘un-Darwinian,’ ” or more-precisely un-Neo-Darwin- ‹ƒDzƒ„‘—––Š‡ Žƒ‹–Šƒ––Š‡”‡ƒ”‡†‡˜‡Ž‘’‡–ƒŽ ‘•–”ƒ‹–•dzȋƒ› - ƒ”†‹–Šͥͤ͟͝ǡ͠͠ȌǤ

•Š‘”–ǡ‹–‹•‘– Ž‡ƒ”Š‘™–Š‹•ƒ”‰—‡– ŠƒŽŽ‡‰‡•–Š‡Ƥ”•–ƒ•’‡ – of the core of the Neo-Darwinian view since in order for the morpho- ‰‡‡–‹ Ƥ‡Ž†–‘„‡–Š‡—‹–‘ˆŠ‡”‡†‹–›ǡ‹–—•–„‡ ƒ’ƒ„Ž‡‘ˆ ‘–ƒ‹ - ‹‰ƒ†’ƒ••‹‰‘ƒ˜ƒ”‹ƒ–‹‘–‘‘ơ•’”‹‰Ǥ ‹”•–ǡ–Š‡ˆƒ ––Šƒ–‹– ‘‡• to dominate only the post-protein production stage is not pertinent to this function, as the structure of the protein has been already altered if mutations have occurred. Second, the externally induced morpho- ‰‡‡–‹ Ƥ‡Ž†Šƒ•Ž‹‹–‡†˜ƒ”‹ƒ„‹Ž‹–›ǤŽ–Š‘—‰Š–Š‹• Šƒ”ƒ –‡”‹•–‹ ‹•ƒ† - vantageous in providing the stability of the morphogenetic processes, ‹–•‡˜‡”•–Š‡Ƥ‡Ž†ǯ• ƒ’ƒ ‹–›ˆ‘”ƒ••‹‹Žƒ–‹‰•‹‰‹Ƥ ƒ–ƒŽ–‡”ƒ–‹‘•ǡƒ• it ƒ‘–„‡•‹‰‹Ƥ ƒ–Ž›ƒŽ–‡”‡†ȋ–Š‡”ƒ‰‡‘ˆ–Š‡Dz‘”†‡”’ƒ”ƒ‡–‡”dz‘ˆ –Š‡Ƥ‡Ž†‡“—ƒ–‹‘•‹•˜‡”›•ƒŽŽȌǤ ‘”†‡”–‘’‡”ˆ‘”–Š‡‹Š‡”‹–ƒ ‡ ˆ— –‹‘ǡ–Š‡Ƥ‡Ž†™‘—Ž†Šƒ˜‡–‘„‡’‘–‡–‹ƒŽŽ›•—ƥ ‹‡–Ž›˜ƒ”‹ƒ„Ž‡ȋƒŽ - ‘•–ƒ•— Š•‘ƒ•‰‡‡•ȌǤŠ—•ǡ†‡•’‹–‡–Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž†ǯ•†‡ - ˜‡Ž‘’‡–ƒŽ•‹‰‹Ƥ ƒ ‡ƒ•ƒ•‡˜‡”‡Ž› ‘•–”ƒ‹‹‰ˆƒ –‘”ǡ˜ƒ”‹ƒ–‹‘•ƒ”‡ due to genes, and more importantly, are passed on by genes .

Š‡‹†— ‡†‘”’Š‘‰‡‡–‹ Ƥ‡Ž†‹‰Š–’‘•‡ƒ‘–Š‡”‘†‡•–ƒ†‹ - †‹”‡ –ǡ„—–•–‹ŽŽ•‹‰‹Ƥ ƒ– ŠƒŽŽ‡‰‡–‘‡–”ƒŽ‘‰ƒǡŠ‘™‡˜‡”ǤŠ—•ǡ –Šƒ– –Š‡ ˜ƒ”‹ƒ–‹‘• ȋ„› —–ƒ–‹‘•Ȍ ƒ– –Š‡ ‘Ž‡ —Žƒ” Ž‡˜‡Ž ƒ”‡ — ‘ - strained might be irrelevant, as the mutations do not result in one-to-one SLOBODAN P EROVIĆ THE REBIRTH OF THE MORPHOGENETIC FIELD

mapping with the actual changes of phenotype: most mutations are idle „‡ ƒ—•‡‘ˆ–Š‡Š‹‰ŠŽ›•–”— –—”‡†ƒ†‹˜ƒ”‹ƒ–‘”’Š‘‰‡‡–‹ Ƥ‡Ž†ǤŠ‡ ‹Š‡”‹–‡† ’ƒ”–‹ —Žƒ”• ȋ ‘Ž‡ —Ž‡•Ȍ ƒ”‡ ‡ƥ ‹‡– ‘Ž› ‹ –Šƒ– –Š‡› •–ƒ„‹Ž‹œ‡’ƒ”–‹ —Žƒ”•‘Ž—–‹‘•‘ˆ‘”’Š‘‰‡‡–‹ Ƥ‡Ž†‡“—ƒ–‹‘•™‹–Š‹ ƒ˜‡”› Ž‹‹–‡†”‡’‡”–‘‹”‡ ȋ ‘‘†™‹ ͥͤ͝͠ǡ ͥ͞͞ȌǤŠ‡‡šƒ’Ž‡‘ˆ Dros- ophila embryos and homeogenic genes might provide more substantial ‡˜‹†‡ ‡–Šƒ––Š‡• ‘’‡‘ˆ’‘–‡–‹ƒŽŽ›‡ơ‡ –‹˜‡‰‡‡–‹ ˜ƒ”‹ƒ–‹‘•ƒ† hence the scope of the genetic program are indirectly but severely con- •–”ƒ‹‡†„›–Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž†ȋ ‹Ž„‡”–ǡ’‹–œƒ†ƒơͥͥ͢͝ǡ͟͢͠Ǧ ͡Ǣ ‘‘†™‹ͥͤ͝͠Ȍǡ 2 thereby rendering the second component of the Cen- tral Dogma irrelevant or at least prompting its thorough reformulation.

‡––Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž††‘‡•‘–‹Š‡”‹––Š‡ƒ –—ƒŽ–”ƒ‹–•™Š‹ Š”‡ - sult from the genetic variations. Strictly speaking, inherited character- 186 istics result from the mutations-selection coupling, irrespective of how severely are mutations constrained. In fact, the view that “declaring the ‘”’Š‘‰‡–‹ Ƥ‡Ž†–‘„‡ƒƒŒ‘”‘†—Ž‡‘ˆ†‡˜‡Ž‘’‡–ƒŽƒ†‡˜‘ - lutionary change is setting it up as an alternative to the solely genetic ‘†‡Ž‘ˆ‡˜‘Ž—–‹‘ƒ††‡˜‡Ž‘’‡–dz ȋ ‹Ž„‡”–ǡ ’‹–œƒ† ƒơ ͥͥ͢͝ǡ ͤ͟͢Ȍ •Š‘—Ž† „‡ –ƒ‡ ™‹–Š ƒ—–‹‘ǡ ‹ˆ „› Dz‡˜‘Ž—–‹‘ƒ”› Šƒ‰‡dz ‘‡ means the production and inheritance of variations. The inherited vari- ƒ–‹‘•ƒ”‡„‘–Š’”‘†— ‡†ƒ†‹Š‡”‹–‡†„›–Š‡‰‡‡•ȋȌǡƒŽ–Š‘—‰Š –Š‡‹”•— ‡••†‡’‡†•‘–Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž†ƒ•ƒƒ††‹–‹‘ƒŽƒŽ„‡ - ‹–†‘‹ƒ–ȋ‹Ǥ‡Ǥǡ–Š‡‘•– ‘•–”ƒ‹‹‰Ȍ‡š–‡”ƒŽˆƒ –‘”Ǥ ‘–Š‡”™‘”†•ǡ –Š‡ ‘ Ž—•‹‘–Šƒ––Š‡‹†— ‡†‘”’Š‘‰‡‡–‹ Ƥ‡Ž††‡Ž‹˜‡”•‘‘—šǯ• prophecy is unsubstantiated.

3. An Anomaly That Won’t Go Away: The Structural Inheritance in Ciliate Protozoa And The Global Cellular Morphogenetic Field

ˆ ƒ›™Š‡”‡ǡ –Š‡ Š‡”‡†‹–ƒ”› ˆ— –‹‘ ‘ˆ –Š‡ ‘”’Š‘‰‡‡–‹  Ƥ‡Ž† is found in ciliate protozoa Ǥ –Š‹• ƒ•‡ǡ–Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž†‹•˜‡”› variable, and as such, it is claimed to inherit the changes that are exter- ƒŽŽ›‹ƪ‹ –‡†‘ƒ†—Ž–‹†‹˜‹†—ƒŽ•Ǥ ƒ„Ž‘ƒȋ͜͜͞͡ǡ͝͞͞Ȍ•—‰‰‡•–•–Š‡ ˆ‘ŽŽ‘™‹‰ȋ”‘—‰ŠŽ›ƒ’’”‘’”‹ƒ–‡ȌƒƒŽ‘‰›ǣDz –™ƒ•ƒ•‹ˆ–Š‡†‡• ‡†ƒ–•‘ˆ a person whose leg had been amputated inherited the same handicap.”

2 ”‹‰ƒ†–ȋͣ͜͜͞Ȍƒ‡•ƒ•‹‹Žƒ”ǡƒŽ–Š‘—‰Š‘”‡‰‡‡”ƒŽ’‘‹–ǡ ‘ ‡”‹‰Š‘‘Ž - ‘‰›ǡ–Šƒ–Š‡†”ƒ™•ƒ‹Ž›ˆ”‘ȋòŽŽ‡”͜͜͟͞ȌǤ ‘™‡˜‡”ǡ–Š‹•™‘”†‘‡•‘–’”‘˜‹†‡ ƒƒ ‘—–‘ˆ–Š‡ƒ –—ƒŽ‡ Šƒ‹••‘ˆ–Š‡ ‘•–”ƒ‹–•ƒ• ‘‘†™‹ǯ•†‘‡•ǡ™Š‹ Š ƒ‡•”‹‰ƒ†–ǯ•ƒ”‰—‡–‘’‡–‘ƒ›ƒ”†‹–Šǯ•‘„Œ‡ –‹‘ȋ‘–‡†‘’ǤͣȌǤ THE NOTION AND STRUCTURE OF EXPLANATION IN THE NATURAL AND SOCIAL SCIENCES

Š‡Ƥ”•–ǡƒŽ–Š‘—‰Š‘––Š‡•–”‘‰‡•–ǡ ƒ•‡‘ˆ–Š‡•—’’‘•‡†•–”— –—”ƒŽ inheritance in ciliates is the well-studied inheritance of inversions of ciliary rows .

‡ ƒ”‘–ƒ–‡ȋ‹˜‡”–Ȍ‡š’‡”‹‡–ƒŽŽ›„›ͤ͜͝Ǧ†‡‰”‡‡•–Š‡ ‘Ƥ‰—”ƒ–‹‘ of ciliary rows in Paramecium tetraurelia and Tetrahymena thermopile , ƒ•™‡ŽŽƒ•–Š‡ ‘Ƥ‰—”ƒ–‹‘‘ˆƒ”‰‹ƒŽ ‹Ž‹ƒ”›”‘™•‹ Stylonychia myti- lus and Paraurostyla weissei . The inverted rows are generated in the so- called fusion of cells-clones with identical nuclei with the “invasion” of ‹Ž‹ƒ”›”‘™•ȋ‹Ǥ‡Ǥǡ‘ˆƒ’ƒ”–‹ —Žƒ” ‘Ƥ‰—”ƒ–‹‘‘”‘”‹‡–ƒ–‹‘‹™Š‹ Š –Š‡›ƪƒ’Ȍˆ”‘–Š‡ ‘”–‡š‘ˆ‘‡ ‡ŽŽ–‘–Š‡ ‘”–‡š‘ˆ–Š‡‘–Š‡”ǤŠ‡†‹˜‹ - •‹‘‘ˆ–Š‡ˆ—•‡† ‡ŽŽ•ȋ–Š‡ ‘Œ—‰ƒ–‹‰ ‡ŽŽ•Ȍ”‡•—Ž–•‹ƒ•‹‰Ž‡–’”‘‰‡› ™‹–Šƒ‹˜‡”–‡† ‹Ž‹ƒ”›”‘™•ȋ‹˜‡”–‡†™‹–Š”‡•’‡ ––‘–Š‡‘”‹‡–ƒ–‹‘‘ˆ cilia prior to the “invasion” from the other cell). 187 ‹Ž‹ƒ”›Ǧ”‘™‹˜‡”•‹‘•ƒ”‡‹Š‡”‹–‡†ˆ‘”‘”‡–Šƒͤ͜͜Ƥ••‹‘•‹ Ž‘‡•ǡ and the nucleus and the DNA in the nucleus seem to play no role. Son- ‡„‘”ȋͥͣ͜͝ǡ͟͟͡Ȍǡ™Š‘’‹‘‡‡”‡†–Š‡•‡•–—†‹‡•‘ơ‡”‡†™Šƒ–™‡‹‰Š– call a strong interpretation of the phenomenon: the molecular cortical geography, whatever its exact structure might be, determines the initia- –‹‘ǡ‹‰”ƒ–‹‘ƒ†‘”‹‡–ƒ–‹‘‘ˆ„ƒ•ƒŽ„‘†‹‡•ȋ‹Ǥ‡Ǥǡ ‹Ž‹ƒȌǡ‘––Š‡‡š - –‡”ƒŽȋ— Ž‡‘–‹ Ȍ‘Ž‡ —Žƒ”‘” ‡ŽŽ—Žƒ”‹ƪ—‡ ‡ǡƒ•— Ž‡‹ƒ”‡‹†‡–‹ ƒŽ in the “invader” and the “invaded” cells. And such molecular geography ‹•”‡•’‘•‹„Ž‡ˆ‘”–Š‡‹Š‡”‹–ƒ ‡‘ˆ–Š‡ ‘Ƥ‰—”ƒ–‹‘‹–Š‡ Ž‘‡•Ǥ

One might doubt the soundness of such an interpretation, and won- †‡”™Š‡–Š‡”–Š‡— Ž‡‹”‡ƒŽŽ›”‡ƒ‹‹†‡–‹ ƒŽǤƒ•‡†‘™Šƒ–™‡‘™ about other similar cases, it could be that the nucleus in the detached cell mutates rapidly upon detachment and is responsible for the inver- •‹‘•ǤŠ‡”‘Ž‡‘ˆ–Š‡— Ž‡—•‹•— Šƒ ƒ•‡™‘—Ž†”‡ƒ‹— Ž‡ƒ”ȋ‡Ǥ‰Ǥǡ why does the result of the mutation coincide with the result of the inva- •‹‘‘ˆ ‹Ž‹ƒˆ”‘–Š‡‘–Š‡” ‡ŽŽǫȌǡ„—–‹–• ‘–‡–™‘—Ž†”‡ƒ‹ƒ‡ơ‡ - tive unit of inheritance.

Š‡”‡‹•ƒ‡š’‡”‹‡–ƒŽƒ•™‡”–‘–Š‹•‘„Œ‡ –‹‘ȋ ”ƒ‡Žͥͤͥ͝ȌǤŠ‡ genetic mutations result in either the appearance of erratic ciliary units outside the rows or the disorganization of the rows, while the ciliato- ”›—‹–•’”‡•‡”˜‡–Š‡‘”ƒŽ’‘•‹–‹‘ȋ”‡Žƒ–‹˜‡–‘ƒ ‡••‘”›•–”— –—”‡•ȌǤ Š‡–Š‡ ‡ŽŽ‡„”ƒ‡‘”‡’‹’Žƒ•‹•†‹•”—’–‡†‘Ž‡ —Žƒ”Ž›ȋ–Š”‘—‰Š mutations) or otherwise, the ciliary units retain their position – unlike in the fusion experiments. SLOBODAN P EROVIĆ THE REBIRTH OF THE MORPHOGENETIC FIELD

˜‡‘”‡•–”‹‹‰‹•‹Š‡”‹–ƒ ‡‘ˆ–Š‡•‘Ǧ ƒŽŽ‡††‘—„Ž‡– ‘Ƥ‰—”ƒ - tion – a functioning unit of two cells fused at the anterior and posterior ‡†•ǤŠ‡†‘—„Ž‡–•ƒ”‡’”‘†— ‡†„›–Š”‡‡†‹ơ‡”‡––‡ Š‹“—‡•ǣƤ”•–ǡ„› the failure of separation of conjugating cells, second, by the spatial ad- Œ—•–‡–•–Šƒ–ˆ‘ŽŽ‘™ƒ””‡•–‡† ‡ŽŽ†‹˜‹•‹‘ǡƒ†ƤƒŽŽ›ǡƒ•ƒ”‡•’‘•‡–‘ microsurgically created fusions. The cells produced by the second and third technique are typically stable. In the inherited homopolar dou- „Ž‡–• ȋ‹Ǥ‡Ǥǡ†‘—„Ž‡–•™‹–Š ‘ Šƒ†‡†‡••Ȍ –Š‡ ‘”’Š‘Ž‘‰›†”ƒ•–‹ ƒŽŽ› Šƒ‰‡•ǡ†‡•’‹–‡–Š‡Žƒ ‘ˆ—–ƒ–‹‘ȋ‹Ǥ‡Ǥǡ‘Ž‡ —Žƒ”Ǧ‰‡‡–‹ ‹ˆ‘”ƒ - tion has not changed): the duplicate sets of surface structures around the common endoplasm lack internal division – we have a doubled cor- tical organization. Now, in the doublets conjugating with singlets, the doublet ex-conjugate gives rise to a doublet clone and the singlet to a singlet, even though the ex-conjugate clones are genetically identical. 188 ‘”‡‘˜‡”ǡ–Š‡— Ž‡ƒ” ‘Œ—‰ƒ–‹‘ 3 can be experimentally accompanied by a massive exchange of internal cytoplasm, thus ruling out the control of the process by organelles. And when the nucleus is divided unequally and imported into doublets and singlets, it grows back to its usual size. ȋ ”ƒ‡Žͥͤͥ͝ǡͤͤǦͥ͝ȌŠ‹• ‘—Ž†‹’Ž›–Šƒ––Š‡†‡˜‡Ž‘’‡–‘ˆ–Š‡— - cleus and its content is controlled by the doublet organization, not vice versa Ǥ –‹•‘–•—”’”‹•‹‰–Š‡ǡ–Šƒ–‘‡„‘”ȋͥ͢͟͝Ȍ ‘ Ž—†‡†ˆ”‘ the study of doublets that the cortex remains the only candidate for the control of development and that it is responsible for inheritance.

Ž–Š‘—‰Š–Š‡•‡ ƒ•‡•‹‰Š–•‡‡†‡Ƥ‹–‹˜‡‡˜‹†‡ ‡ˆ‘”–Šƒ––Š‡ does not play a role in cortical inheritance, this understanding can be questioned at a more general level. In fact, the entire case might be deemed essentially irrelevant to what we normally regard as inherit- ƒ ‡Ǥ ‹”•–ǡ –Š‡ — Ž‡‹  ƒ–‡”‹ƒŽ• ȋ‹Ǥ‡Ǥǡ  ƒ† Ȍ ƒ”‡ –Š‡ „ƒ•‹  ‘–”‘ŽŽ‡”•‘ˆ–Š‡’”‘ ‡••–Šƒ–‰‘˜‡”•–Š‡ Šƒ‰‡•‹ ‘Ƥ‰—”ƒ–‹‘‘ˆ basal bodies: they synthesize the cortical proteins and enable reproduc- tion after all. Second, the peculiarities of the “cortical inheritance” do nothing to question the basic premise of the Central Dogma: rather, –Š‡ ‘Ƥ‰—”ƒ–‹‘•‘ˆ„ƒ•ƒŽ„‘†‹‡•ƒ”‡‘–Š‹‰„—– peculiar examples of variations of multiplicity or orientation of structural patterns while the internal cellular structure and functions remain the same . Although, the above cases are puzzling, once could argue that they are independent

3 Singlet ciliates have two nuclei, macro and micro-nucleus. Doublets will have either one or two macronulei. As a matter of fact, the number of doublets with one — Ž‡—•†‡ ”‡ƒ•‡•™‹–Š•—„•‡“—‡–Ƥ••‹‘•ƒ†–Š‡ ‘–‡–‹•͜͡–‘͜͜͝τŽƒ”‰‡” than in the macronucleus of a singlet. THE NOTION AND STRUCTURE OF EXPLANATION IN THE NATURAL AND SOCIAL SCIENCES

from the understanding of what one would label inheritance – unless of course one were to adopt an idiosyncratic and insubstantial notion of it.

The study of inheritance in certain types of the doublets, however, clear- ly shows that such an assessment is on the wrong track. The inheritance ‘ˆ–Š‡‹˜‡”–‡†ȋ”ƒ–Š‡”–Šƒ‡”‡Ž›”‡˜‡”•‡†ȌŽƒ”‰‡Ǧ• ƒŽ‡•›‡–”›‹ the so-called type III doublets is substantial, as the heritable mirror-im- age global inversion ƒơ‡ –•–Š‡‹–‡”ƒŽ‘”‰ƒ‹œƒ–‹‘‘ˆ–Š‡‘”’Š‘‰‡ - netic system (really the entire cell) and its functionality ȋ ”ƒ‡Ž͜͜͜͞ǡ 93). The cortical bodies of one of the genetically identical “semicells” in •— Šƒ†‘—„Ž‡–ƒ”‡Ž‡ˆ–ǦŠƒ†‡†ǤŠ‹•ƒơ‡ –•–Š‡‹”ˆ— –‹‘ƒŽ‹–›ȋƒ†–Šƒ– ‘ˆ–Š‡‹” Ž‘‡†‘ơ•’”‹‰Ȍ™Š‡•‡’ƒ”ƒ–‡†ˆ”‘–Š‡†‘—„Ž‡–ǡƒ•–Š‡‘”ƒŽ ‡„”ƒ‡ŽŽ‡•–Šƒ– ‘–”‘Ž–Š‡ƪ‘™‘ˆ™ƒ–‡”‹ˆ‡‡†‹‰ƒ”‡‹˜‡”–‡†ƒ† sweep the food away from the oral pouch, and the subsequent DNA- based reorganizations of the internal structure, quite common in cili- 189 ƒ–‡•ǡ ƒ‘– Šƒ‰‡–Š‡’‘Žƒ”‹–›ȋŽ‡ˆ–ǦŠƒ†‡†‡••Ȍ‘ˆ–Š‡ ‡ŽŽǤ ‹ƒŽŽ›ǡ the right-handed semi-cell will propagate the right-handedness in its ‘ơ•’”‹‰ǡ™Š‹Ž‡Ž‡ˆ–ǦŠƒ†‡†‡••™‹ŽŽ„‡’”‘’ƒ‰ƒ–‡†‹–Š‡‘ơ•’”‹‰‘ˆ the dysfunctional cell, despite the identical nucleus.

One could also argue that “[m]ost cases of ‘cytoplasmatic’ inheritance turn out to depend on non-nuclear DNA and RNA, a fact which encour- ages a still more gene-centered and less organism-centered view of evo- Ž—–‹‘dzȋƒ›ƒ”†‹–Šǡͥ͟ȌǤ

No traces of DNA molecules have been found in the cortex of ciliates. Still, it is possible to speculate that an explanation of these processes is available at the level of the cortex: cortical RNA might be responsible for patterning and turn out to be the unit of heredity. Indeed, the RNA ‘Ž‡ —Ž‡•Šƒ˜‡„‡‡†‹• ‘˜‡”‡†‹–Š‡ ‘”–‡šǤ‡–‡š ‡‡†‹‰Ž›†‡–ƒ‹Ž‡† •–—†‹‡•‘ˆ ‹–• ˆ— –‹‘ ȋ‡Žƒ––”‡ǡ ‘”ƒ†ƒ† ڐ œ›ǡ͜͜͢͞Ǣ ‡ŽŽ‡–‹‡” ‡–ƒŽǤǡ͜͜͢͞ȌŠƒ˜‡•Š‘™–Šƒ–‹– ƒ‘–ƒ ‘—–ˆ‘”–Š‡‰‡‘‡–”›‘ˆ–Š‡ propagation of ciliary rows – what turns out to be, as we will see short- ly, only an intermediary level of the structure that governs development and inheritance. 4 And it is even less likely that it will account for the in- dispensable of –Š‡‰Ž‘„ƒŽ‘”’Š‘‰‡‡–‹ Ƥ‡Ž†–Šƒ– ‘–”‘Ž•–Š‡†‡˜‡Ž‘’ - ment and inheritance of ciliates by controlling polarity of the cell .

4 It seems that RNA plays only a secondary role in mediating the epigenetic “program” which directs the disintegration of DNA in morphogenetic processes. ȋ‘™ƒ ‹‡–ƒŽǤǡͣ͜͜͞Ȍ SLOBODAN P EROVIĆ THE REBIRTH OF THE MORPHOGENETIC FIELD

The explanation of both the development and inheritance of large-scale organization found in Oxytricha and Stylonychia doublets requires •— Šƒ‰Ž‘„ƒŽ ‡ŽŽ—Žƒ”‘”’Š‘‰‡–‹ Ƥ‡Ž†ǤŠ‡•‡ ‹Ž‹ƒ–‡• ƒ—†‡”‰‘ the stage of the cyst which incurs a complete loss of the internal cellu- Žƒ”•–”— –—”‡Ǥˆ–‡”†‡†‹ơ‡”‡–‹ƒ–‹‘ƒ––Š‡ ›•–•–ƒ‰‡ǡƒ‘”ƒŽ ‹Ž‹ƒ–—”‡ ‹•†‡˜‡Ž‘’‡†Ǥ‡––Š‡•’‡ ‹Ƥ Ž‘ ƒŽǦ•–”— –—”ƒŽ‹ˆ‘”ƒ–‹‘‘ˆ–Š‡ ‘”–‡š disappears during the cyst stage. That is why the extra marginal rows that are propagated for several vegetative cell generations complete- ly disappear after the cyst stage. They should not do so if these local structures are preserved and responsible for the post-cyst development ȋ ”ƒ‡Žͥͤͥ͝ǡͤͥǦͥ͜ȌǤ‘”‡‘˜‡”ǡ–Š‡’ƒ”–•‘ˆ–Š‡‡“—ƒ–‘”‹ƒŽŽ›–”ƒ•ƒ – - ed doublet of a certain type will produce the doublets of the same type ™‹–Š ‘’Ž‡–‡ ‹Ž‹ƒ–—”‡•ȋ‹„‹†ǤǢ ”ƒ‡Ž͜͜͜͞ȌǤ

190 ‡–†‡•’‹–‡ƒ˜‡”›Ž‹‹–‡†”‡Ž‡˜ƒ ‡‘ˆŽ‘ ƒŽ•–”— –—”‡ǡ†‘—„Ž‡–•„”‘—‰Š– –‘ ›•–•–ƒ‰‡‡š ›•–ƒ•†‘—„Ž‡–•ȋ‡Ǥ‰Ǥǡƒ†‘—„Ž‡– –›’‡‡‡”‰‡•ƒ•ƒ†‘— - blet III type, not as a singlet, despite their identical nuclei), whose ge- ‘‡–”›ȋ’‘Žƒ”‹–›Ȍ‹•’”‡•‡”˜‡†Ǥ•ƒŽŽ–Š‡•‡•–”— –—”ƒŽ Šƒ‰‡•ƒơ‡ –‹‰ –Š‡ ‘”–‡šƒ”‡’”‘’ƒ‰ƒ–‡†‹–Š‡‘ơ•’”‹‰ǡ‘‡ ƒ‘–‡• ƒ’‡–Š‡ ‘ - clusion that the cortical RNA can hardly be the silver-bullet, as the local cortical structure itself is irrelevant to such changes. One is led to con- clude that “something global” must be inherited.

Indeed, the global polarity in ciliates exhibits supremacy over the cy- –‘•‡Ž‡–ƒŽ’‘Žƒ”‹–›Ǥ –‹•”‡•’‘•‹„Ž‡ˆ‘”–Š‡Ƥ‡’‘•‹–‹‘‹‰‘ˆ’ƒ‹”•‘ˆ contractile vacuole pores, as well as the position of mitochondria mi- crotubule bands and the anterior structures. In addition, the change of ‰Ž‘„ƒŽ’‘Žƒ”‹–›‹•ƒȋ—Ž–‹Ȍˆ— –‹‘ƒŽ Šƒ‰‡ȋ ”ƒ‡Ž͜͜͜͞ȌǤ

In sum, there are three distinct levels responsible for patterning de- ˜‡Ž‘’‡–ǣ –Š‡ ‘Ž‡ —Žƒ” Ž‡˜‡Žǡ –Š‡ ‹–‡”‡†‹ƒ”› Ž‡˜‡Ž ȋ‹ ”‘–—„—Ž‡ „ƒ†•Ȍƒ†–Š‡‰Ž‘„ƒŽŽ‡˜‡Žȋ–Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž†ȌǤŠ‡Žƒ•–Ž‡˜‡Žǡ to be discussed at the greater length in the next section, is dominant, ‘•– Ž‹‡Ž› ‘‡ Šƒ‹ ƒŽ ƒ† Š‡”‹–ƒ„Ž‡ ȋ ”ƒ‡Ž ͜͜͜͞ǡ ͥͣǢ ”ƒ‡Ž ͥͤͥ͝ǡͥ͞ȌǤŠ‡‘Ž‡ —Žƒ”Ž‡˜‡Ž‘ˆ ‘–”‘Ž‹•‹””‡Ž‡˜ƒ–ˆ‘”ƒ ‹Ž‹ƒ”›—‹–•ǯ patterning. RNA has only a mediating function in cortically-controlled inheritance in ciliates, while DNA does not seem to contribute at all.

As for the molecular basis of the origin of global polarity, some inter- ‡•–‹‰•—‰‰‡•–‹‘•‹˜‘‡–Š‡„‹‘Ǧ Š‡‹ ƒŽƤ‡Ž†ȋ ”ƒ‡Ž͜͜͜͞ǡͥͥ͝͝Ȍǡ where chemical substances acquire morphogenetic functions in the ‘–‡š– ‘ˆ –Š‡ ‡ŽŽ ȋ‡Ǥ‰Ǥǡ Ž‹–Š‹— ƒ “—‹”‡• ƒ ‡™ ˆ— –‹‘ ™‹–Š‹ –Š‡ THE NOTION AND STRUCTURE OF EXPLANATION IN THE NATURAL AND SOCIAL SCIENCES

existing spatial circumferential structure). This is quite the opposite of –Š‡‹†— ‡†‘”’Š‘‰‡‡–‹ Ƥ‡Ž†Ǥ

Š‡ƒ––‡’–•–‘ˆ‘”ƒŽ‹œ‡–Š‡‰Ž‘„ƒŽ‘”’Š‘‰‡‡–‹ Ƥ‡Ž†‹ ‹Ž‹ƒ–‡•”‡Ž› ‘–Š‡ ‘„‹ƒ–‹‘‘ˆ–Š‡’‘Žƒ”ƒ’•ȋƒ†’‘Žƒ” ‘‘”†‹ƒ–‡‘†‡Ž•Ȍ which trace the assembly processes, along with the positional informa- –‹‘ƒ†Œ—•–‡†–‘–Š‡•’‡ ‹Ƥ ’”‘ ‡••‡•‹ ‹Ž‹ƒ–‡•Ǥ 5ƒ–‡•‘ǯ•‹†‡ƒ‘ˆ–Š‡ ’”‹ ‹’Ž‡‘ˆ‹–‡‰”ƒ–‹‘ȋƒ–‡•‘ͤͥ͝͞ȌŠƒ•„‡‡”‡˜‹˜‡†ǡƒ•™‡ŽŽǤ –ƒ - counts for a system whereby the anatomy of the elements depends on –Š‡‹”Ž‘ ƒ–‹‘”‡Žƒ–‹˜‡–‘–Š‡˜ƒ”›‹‰’”‘’‡”–›‘ˆ–Š‡Ƥ‡Ž†Ǣ‹ ‹Ž‹ƒ–‡•ǡˆ‘” ‡šƒ’Ž‡ǡ–Š‡—–—ƒŽ ‘Ƥ”ƒ–‹‘™‹–Š‹ƒ•‡–‘ˆ‡„”ƒ‡ŽŽ‡•‹•‘”‡ important than their individual structure.

Ž–Š‘—‰Š‹–‹• Ž‡ƒ”–Šƒ–‘†‡”›–Š‡•‹• ƒ„‡‘ˆŽ‹––Ž‡Š‡Ž’ƒ• plays only a minor regulative role, the nature of both the global mor- ’Š‘‰‡‡–‹ Ƥ‡Ž†ƒ† Dz–Š‡ ‡••ƒ‰‡dz”‡•’‘•‹„Ž‡ˆ‘”†‡˜‡Ž‘’‡–ƒ† 191 inheritance is far from being understood. The ciliate morphogenetic Ƥ‡Ž†‹•‘”‡˜ƒ”‹ƒ„Ž‡–Šƒ‡‹–Š‡”–Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž†ƒ•‹–™ƒ•–”ƒ - †‹–‹‘ƒŽŽ› ‘ ‡‹˜‡†ǡ‘”–Š‡‹†— ‡†‘”’Š‘‰‡‡–‹ Ƥ‡Ž† ‘—Ž†„‡ǡ„—– ƒ• ”ƒ‡Žȋͥͥ͝͝Ȍ‘–‡•ǣ We can only guess at the medium within which the patterning in- structions reside: is it a cell membrane, the epiplasmatic layer … or some gelated ectoplasm underneath that? … And as for the message, ƒ”‡™‡–ƒŽ‹‰ƒ„‘—–†‹ơ‡”‡–‘Ž‡ —Ž‡•ǡȋ’”‘–‡‹•ǫ‡”Šƒ’•ƒφφ ‹‘•ǫȌ–Šƒ–ƒ”‡‘„‹Ž‡ǡ‘”’‘••‹„Ž›‘ˆ‡“—ƒŽŽ›‘„‹Ž‡•–ƒ–‡•‘ˆ‘†‹Ƥ - ƒ–‹‘‘ˆ’”‘–‡‹•ǥ‘”•‘‡–Š‹‰‡Ž•‡ƒŽ–‘‰‡–Š‡”ǫȋ ”ƒ‡Žͥͥ͝͝ǡ͡͞͠Ȍ

Thus, one needs to talk about the dynamic change-sensitive property ‘ˆ–Š‡•›•–‡ȋ ”ƒ‡Ž͜͜͜͞ǡͥ͝Ȍǡƒ†–Š‡„ƒ•ƒŽ„‘†‹‡•—•–„‡—†‡” - stood as global structural templates , not as informational in the sense ‘ˆ–Š‡ƒ•‹ˆ‘”ƒ–‹‘ƒŽ—‹–ȋ ”ƒ‡Ž͜͜͜͞ǡͥ͜ȌǤŠ‡Ǧ„ƒ•‡† molecular approach to the unit of inheritance expects the analysis of molecular structure to reveal the message. In the case of the morphoge- ‡–‹ Ƥ‡Ž†‹ ‹Ž‹ƒ–‡•ǡ–Š‡Ƥ‡Ž†ƒ’’”‘ƒ Š’”‘‹•‡•ƒ••‡„Ž‹‰–Š‡•–”— - –—”‡ȋ‹–‡”•‘ˆ•’ƒ–‹ƒŽ”‡Žƒ–‹‘•ƒ†’‘Žƒ”‹–›Ȍ™‹ŽŽ”‡˜‡ƒŽ–Š‡‡••ƒ‰‡Ǥ

Ž–Š‘—‰Š–Š‡†‹”‡ – ‘‡ –‹‘„‡–™‡‡’Š›•‹ ƒŽƒ†„‹‘Ž‘‰‹ ƒŽƤ‡Ž†• is not likely to produce any interesting results, analogies between the two might be a good starting point. Such analogies would raise a number of potentially insightful questions. To start with: is the global

5 The cell signalling initially accounted for the inter-cell communication in cascad- ‹‰’ƒ––‡”‹‰–Šƒ–™ƒ•‰‘˜‡”‡†„›–Š‡‰‡‡–‹ ȋȌ‹ˆ‘”ƒ–‹‘Ǥ ‘™‡˜‡”ǡ–Š‡”‡ is no such information in the processes in ciliates. SLOBODAN P EROVIĆ THE REBIRTH OF THE MORPHOGENETIC FIELD

‘”’Š‘‰‡‡–‹ Ƥ‡Ž†ƒ‡••‡–‹ƒŽŽ› ‘–‹—‘—•‘”†‹• ”‡–‡‡†‹—ǫ ˆ –Š‡ˆ‘”‡”‹•–”—‡ǡ™‹ŽŽ‡ Šƒ‹ ƒŽ–Š‡‘”‹‡•‘ˆ ‘–‹—‘—•‡†‹—ȋ‹ - ˜‘Ž˜‹‰˜‡Ž‘ ‹–›ǡƒ ‡Ž‡”ƒ–‹‘ǡ†‹•’Žƒ ‡‡–ǡƒ†•–”‡••Ȍ•—ƥ ‡ǫ”‹• ƒ†‡˜‡Ž‘’‡–‘ˆ‘Ǧ‡ Šƒ‹ ƒŽƤ‡Ž†–Š‡‘”‹‡•”‡“—‹”‡†ǫ‹ŽŽƒ˜‡ - –‘”ƒƒŽ›•‹•„‡•—ƥ ‹‡–ȋ—‹–‰‡‘‡–”›˜‡ –‘”•ƒ”‡—•‡†‹–Š‡ƒƒŽ› - •‹•‹ȋ ”ƒ‡Žͥͥ͝͝ȌȌǡ‘”•Š‘—Ž†‘‡ƒ’’”‘ƒ Š‹–™‹–Š–‡•‘”ƒ ‘—–• ȋ”ƒ†–•ƒ† ‘–ƒˆ—”‘ ͥͥͣ͝Ȍǫ ‘—Ž† •— Šƒ ‘”’Š‘‰‡‡–‹  Ƥ‡Ž† „‡ treated as essentially permanent or is it variable? It seems that the latter ‹•–Š‡ ƒ•‡ǡ„—–‘”‡‡š’‡”‹‡–ƒŽ•–—†‹‡•ƒ”‡‡‡†‡†Ǥ ”ƒ‡Žȋͥͤͥ͝ǡ ͞͠͝Ȍƒ”‰—‡•–Šƒ––Š‡‘”’Š‘Ž‘‰‹ ƒŽƤ‡Ž†•Š‘—Ž†„‡–”‡ƒ–‡†ƒ•ƒ–‡•‘ǯ• Ƥ‡Ž†ȋ ”ƒ‡Žͥͤͥ͝ǡ͞͠͝Ȍ™Š‹Ž‡‘–Š‡”•ȋ ‹Ž„‡”–ǡ’‹–œƒ†ƒˆ–ͥͥ͢͝ǡͥ͟͡Ǣ ƒŽ‡ƒ†‘•ƒ™ƒͥͥ͜͝Ȍ•—‰‰‡•––Šƒ–ƒ ‘’ƒ”‹•‘™‹–Š‡Ž‡ –”‘ƒ‰‡–‹  Ƥ‡Ž†™‘—Ž†„‡ƒ†˜ƒ–ƒ‰‡‘—•Ǥ

192 4. A New Wave Biology?

The structural inheritance in ciliates might be the most compelling ex- ’‡”‹‡–ƒŽƒ”‰—‡–ƒ‰ƒ‹•––Š‡‡–”ƒŽ‘‰ƒǤ—–„‡ˆ‘”‡™‡‡šƒ - ine this challenge more closely, it is important to emphasize that the ‘”’Š‘‰‡‡–‹ Ƥ‡Ž†ƒ•–Š‡—‹–‘ˆ‹Š‡”‹–ƒ ‡‹ ‹Ž‹ƒ–‡•‹•‘–ƒ–‘††• with Darwinism as such. One might interpret inheritance in ciliates as ‹Š‡”‹–ƒ ‡‘ˆƒ “—‹”‡† Šƒ”ƒ –‡”‹•–‹ •ȋ™‘ơͥͥ͜͝Ȍǡ„—–ƒ–—”ƒŽ•‡Ž‡ - tion can act on such acquired traits. Rather, such inheritance is at odds ™‹–Š–Š‡‰‡”Ǧ ‡–”‹•‘ˆ‘†‡”›–Š‡•‹•Ǥ

Roughly speaking, there are three attitudes towards the Central Dogma ƒ†‹–••‹‰‹Ƥ ƒ ‡Ǥ

Š‡ Ƥ”•– ƒ––‹–—†‡  ™‹ŽŽ ƒŽŽ evolutionary pluralism .6 Although they ‹‰Š–†‹•ƒ‰”‡‡‘–Š‡†‡–ƒ‹Ž•ǡ’Ž—”ƒŽ‹•–•„‡Ž‹‡˜‡–Šƒ–•—„•–ƒ–‹ƒŽŽ›†‹ơ‡” - ent mechanisms of inheritance and, thus, units of selection are at play ‹‡˜‘Ž—–‹‘ƒ†–Šƒ–‰‡‡–‹ Ž‡˜‡Ž‹•‘Ž›‘‡‘ˆ–Š‡ȋ ƒ„Ž‘ƒ͜͜͞͡Ǣ òŽŽ‡”͜͜͟͞Ǣ›ƒƒ͜͜͜͞Ǣ‡ŽŽ‡”͜͜͜͞ǡ‘•‡ͥͥͣ͝Ǣ ƒ„Ž‘ƒƒ†œƒ–Š - máry 1995).

Acknowledging the diversity of the mechanisms of inheritance, the plu- ralist would be wary of drawing any general, let alone universal, conclu- •‹‘•ˆ”‘–Š‡ ƒ•‡‘ˆ ‹Ž‹ƒ–‡•ƒ†–Š‡”‘Ž‡‘ˆ–Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž†Ǥ  their view, the structural inheritance in ciliates is not a counter example

6  –•Š‘—Ž†„‡†‹•–‹‰—‹•Š‡†ˆ”‘’Ž—”ƒŽ‹•–‹ ‰‡‹ •‡Ž‡ –‹‘‹•ƒ•†‡Ƥ‡†‹”ƒ - †‘ƒ†‹ŒŠ‘—–ȋͣ͜͜͞Ȍǡ–Š‡˜‹‡™–Šƒ–•‡Ž‡ –‹‘–ƒ‡•’Žƒ ‡ƒ–Ž‡˜‡Ž•‘–Š‡”–Šƒ–Š‘•‡ of DNA, but always at the level of DNA. THE NOTION AND STRUCTURE OF EXPLANATION IN THE NATURAL AND SOCIAL SCIENCES

to a universal account of inheritance, as there is no such account. In ˆƒ –ǡ –Š‡ ‘”’Š‘‰‡‡–‹  Ƥ‡Ž† ƒ ’‡ƒ ‡ˆ—ŽŽ› ‘‡š‹•– ™‹–Š ‡†‡Ž‹ƒ ‘Ž‡ —Žƒ”‡ Šƒ‹••ȋƒ†ƒͥͥ͝͝ǡ͞ȌǤ‘”‡‘˜‡”ǡƒ–Ž‡ƒ•–•‘‡’Ž— - ralists would acknowledge that the evidence for the pervasiveness of in- heritance best accounted for in Neo-Darwinian terms is overwhelming, and that structural inheritance is merely a ripple in the Neo-Darwinian ™ƒ˜‡Ǥ‡–—Ž‹‡–Š‡ƒŽ–‡”ƒ–‹˜‡•–‘–Š‡‘†‡”›–Š‡•‹•–Šƒ–„”‘ƒ†‡ the gene-centric notion of mechanisms and units of inheritance and •‡Ž‡ –‹‘ ȋ‡Ǥ‰Ǥǡ ›ƒƒ ͜͜͜͞Ȍ Ȃ–›’‹ ƒŽŽ›–Š‡ˆ‘ —•‘ˆ’Š‹Ž‘•‘’Š‡”•‘ˆ „‹‘Ž‘‰›ȋ‡Ǥ‰Ǥ ‘†ˆ”‡›Ǧ‹–Š͜͜͜͞ǢŠ‘’•‘ͣ͜͜͞ȌȂ–Š‡ ƒ•‡‘ˆ ‹Ž‹ - ates renders the gene-centric mechanism irrelevant or introduces “re- versed” genetic processes where DNA is determined by epigenetic pro- grams and inherited as such.

Those who take the Central Dogma as an articulation of a universal 193 ‡ Šƒ‹• ‘ˆ ‹Š‡”‹–ƒ ‡ ƒ† –Š‡ —‹– ‘ˆ •‡Ž‡ –‹‘ ȋƒ™‹• ͥͥ͝͡ǡ ͥͤ͝͞Ǣ ƒ›ƒ”† ‹–Š ͥͤ͝͠Ȍƒ”‡ ˆƒ ‡†™‹–Šƒ — Š ‘”‡†‡ƒ†‹‰ task. The unitarian has to accommodate any apparent exceptions that might serve as counter examples to the Central Dogma. In practical terms, other alternatives to gene-based inheritance can be accommo- dated, or at the very least, there are some interesting ideas as to how this could be done. Not in the case of ciliates, however. This is why the warn- ‹‰‹••—‡†„› ‘Š›ƒ”†‹–Š•Š‘—Ž†„‡–ƒ‡•‡”‹‘—•Ž›‡•’‡ ‹ƒŽŽ› by unitarians: the case of the ciliates runs counter to the core tenets ‘ˆ–Š‡‡–”ƒŽ‘‰ƒǤ‹‹Žƒ”Ž›ǡ ‘‘†™‹™ƒ”•–Šƒ–Dzƒ•‹’Ž‡ ‘— - ter-example [to genocentric biology] comes from the work of Sonne- „‘”ƒ†‘–Š‡”•‹ ‹Ž‹ƒ–‡’”‘–‘œ‘ƒdzȋ ‘‘†™‹ͥͤ͝͠ǡ͞͞͡ȌȌǤŠ‹••Š‘—Ž† prompt unitarians to wonder whether they should become pluralists if the anomaly persists and turns into a full-blown alternative.

Š‡‡‡—‹–ƒ”‹ƒ•Ž‹‡ ‘Šƒ›ƒ”†›–Šƒ›„‡”ƒ”‡Ǥ‘•–’”‘’‘ - nents of the Central Dogma advocate a softer view, treating the Dogma as a fruitful research program that has repeatedly proved its superiority ‘˜‡”‘–Š‡”ƒŽ–‡”ƒ–‹˜‡•ȋ‹ Š‘†ͥͤ͝͝ȌǤ

—––Š‡ ƒ•‡‘ˆ ‹Ž‹ƒ–‡•ƒ›Šƒ˜‡•‡”‹‘—• ‘•‡“—‡ ‡•ǡ‡˜‡ˆ‘”–Š‘•‡ who take such a pragmatic approach.

Rather than asking whether a research program is fruitful, we should ask whether it is advanced in a way that makes it a fruitful program . There are, what one might call internal and external criteria of judging whether a research program is fruitful and to what extent. A program’s SLOBODAN P EROVIĆ THE REBIRTH OF THE MORPHOGENETIC FIELD

™‹†‡ƒ’’Ž‹ ƒ„‹Ž‹–›‹•ƒ‹–‡”ƒŽ ”‹–‡”‹‘ƒ•‹– ‘Ƥ”•–Š‡’‘™‡”‘ˆ ƒ†ƒ†˜ƒ ‡•‹–•‡š’Žƒƒ–‘”›‡ Šƒ‹•Ǥ‡–ƒ’”‘‰”ƒ•Š‘—Ž†ƒŽ•‘„‡ judged on whether, and to what extent, it confronts hard cases as well as emerging alternatives, or if it bypasses and ignores them. This consti- tutes an external criterion.

•™‡Šƒ˜‡•‡‡ǡ–Š‡•–”— –—”ƒŽ‹Š‡”‹–ƒ ‡‹ ‹Ž‹ƒ–‡•‹•ƒȋ˜‡”›ȌŠƒ”† case that should worry those with pragmatic attitude to the Central Dogma as well, but is it a full-blown alternative to the Central Dogma? •‹–’Žƒ—•‹„Ž‡–‘ Žƒ‹–Šƒ––Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž†‹•ƒ’‡”˜ƒ•‹˜‡—‹– of inheritance? Could it undermine the claim of the pervasiveness and relevance, not only of universality, of the Neo-Darwinist mechanisms of inheritance?

‹˜‡ –Š‡ ˆ‘” ‡ˆ—Ž‡•• ‘ˆ –Š‡ ƒ•‡ ˆ‘” –Š‡ ‘”’Š‘‰‡–‹  Ƥ‡Ž† ƒ• –Š‡ 194 vehicle of inheritance in ciliates, it is not surprising that claims con- ‡”‹‰ –Š‡’‘••‹„‹Ž‹–›‘ˆƒ ‹Ƥ‡† ‘”’Š‘‰‡–‹  ‹‡Ž†Š‡‘”› Šƒ˜‡ emerged. Such a theory could concern development and inheritance in both ciliates and eggs Ǥ ”ƒ‡Žȋͥͤ͝͞ǡ͟͝͞Ȍ‡š’Ž‹ ‹–Ž›’—”•—‡•–Š‹•“—‡• - tion by comparing the case of structural inheritance and development in ciliates with the classical case of the inheritance and development of the frog egg. Other studies concentrate on the properties of the mor- ’Š‘‰‡‡–‹ Ƥ‡Ž†‘ˆ–Š‡‹†™‡Ƥ†‹ ‹Ž‹ƒ–‡•ǡ‹‘–Š‡”•’‡ ‹‡•‹ Ž—† - ‹‰”‘•‘’Š‹Žƒȋ¡ŠŽ‡”ƒ†‡–‡”͜͜͜͞ȌǤ

‘‘†™‹ƒ†‡„•–‡”ȋͥͤ͝͞Ǣ•‡‡ƒŽ•‘ ‘‘†™‹ͥͤ͝͠Ȍƒ”‰—‡ˆ‘”–Š‡‘” - ’Š‘‰‡‡–‹ Ƥ‡Ž†ƒ•‰‡‡”ƒ–‹‰ Šƒ‰‡•‹’Š‡‘–›’‡ǡ„—––Š‡‹”ƒ”‰— - ment is weak if it relies on the concept of the induced morphogenetic Ƥ‡Ž†Ǥ‹‹Žƒ” Žƒ‹• ‘‡ˆ”‘–Š‘•‡ƒ”‰—‹‰ˆ”‘Š‘‡‘–‹ ‰‡‡•ȋ ‹ - „Ž‡”–ǡ’‹–œƒ†ƒˆ–ͥͥ͢͝ȌǤ‡–‹–‹•Šƒ”†–‘Œ—•–‹ˆ›‰‡‡”ƒŽ ‘ Ž—•‹‘• ƒ„‘—––Š‡’‡”˜ƒ•‹˜‡‡••ƒ††‘‹ƒ–”‘Ž‡‘ˆ–Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž†ǡ given the limitations I have already pointed out.

Ž–Š‘—‰Š —‹Ƥ ƒ–‹‘ ‹• ƒ ‘„Ž‡ ‰‘ƒŽ ‹ˆ ‘‡ „‡Ž‹‡˜‡• ‹ –Š‡ —‹–› ‘ˆ • ‹‡ ‡ȋ•Ȍƒ†ƒ–—”ƒŽ’Š‡‘‡ƒǡ‰‹˜‡–Š‡•–ƒ‰‡‘ˆ”‡•‡ƒ” Š‹–Š‡ Ƥ‡Ž†ǡ‘‡•Š‘—Ž†‡š’‡ ––Š‡‡‡”‰‡ ‡‘ˆƒ —„‡”‘ˆ†‹˜‡”•‡ ‘” - ’Š‘‰‡‡–‹ Ƥ‡Ž†ƒ ‘—–•Ǥ –‡”‡•–‹‰Ž›ǡ–Š‡•–ƒ–‡‘ˆƒơƒ‹”•‹–Š‹•Ƥ‡Ž† resembles what was happening with respect to magnetic and electric phenomena at Faraday’s time. Thus, there is a great deal of elaborate experimental testing going on, that produces substantial results which ƒ”‡‹ ”‡ƒ•‹‰Ž›”‡˜‡ƒŽ‹‰–Š‡•—’‡”‹‘”‹–›‘ˆ–Š‡Ƥ‡Ž†ƒ’’”‘ƒ Š‘˜‡”–Š‡ †‘‹ƒ– ƒŽ–‡”ƒ–‹˜‡ȋ•Ȍǡ ™Š‹Ž‡ –Š‡ •–—†‹‡† ’Š‡‘‡ƒ ”‡ƒ‹ ‘Ž› THE NOTION AND STRUCTURE OF EXPLANATION IN THE NATURAL AND SOCIAL SCIENCES

Ž‘‘•‡Ž›”‡Žƒ–‡†ǡ™‹–Š‘—–ƒ—‹ˆ›‹‰‰‡‡”ƒŽˆ‘”ƒŽ–Š‡‘”›‘ˆ–Š‡Ƥ‡Ž†–‘ ‘‡ ––Š‡ȋ†‡•’‹–‡ƒ––‡’–•–‘’”‘˜‹†‡•— Šƒ–Š‡‘”›„›—–‹Ž‹œ‹‰ ‘—”‘™Ž‡†‰‡‘ˆ‘™’Š›•‹ ƒŽƤ‡Ž†•ȌǤ

†‹––‡†Ž›ǡ‹– ‘—Ž†–—”‘—––Šƒ––Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž†ƒ†•–”— - tural inheritance are pervasive or even basic, and that ciliates are at the forefront only because they present a suitable case for researching the ‘”’Š‘‰‡‡–‹ Ƥ‡Ž†ǤŠ‡‡š’‡”‹‡–ƒŽ”‡•‡ƒ” Š‘ˆ ›–‘•‡Ž‡–‘‹•’‡ - cies other than ciliate protozoa may reveal a very broad evolutionary •‹‰‹Ƥ ƒ ‡‘ˆ–Š‡‘”’Š‘‰‡‡–‹ Ƥ‡Ž†ȋ”ƒ›͜͜͞͝ǡ͢͡Ǧ͢͜Ǣ¡ŠŽ‡”ƒ† ‡–‡”͜͜͜͞Ǣ”‡‹•ƒ†ƒŽ‡ͥͥͥ͝ǡŠƒŽ‡”ƒ†ƒ‘ͥͥ͢͝ȌǤ

Regardless, the attention dedicated to the case of ciliates by those work- ‹‰™‹–Š‹–Š‡”ƒ‹Ƥ ƒ–‹‘•‘ˆ‘†‡”›–Š‡•‹•ƒ›„‡ƒ‰‘‘†‡ƒ• - ure of the program’s fruitfulness in terms of the external criterion: a lack ‘ˆ•—ƥ ‹‡– ‘•‹†‡”ƒ–‹‘‘ˆ–Š‡ ƒ•‡•Ž‹‡ ‹Ž‹ƒ–‡•™‘—Ž†”‡†‡”‘† - 195 ern Synthesis a fruitful research program only in a very limited sense. ‘™‡˜‡”ǡ™Š‡–Š‡”•— Š•—ƥ ‹‡– ‘•‹†‡”ƒ–‹‘‹•Žƒ ‹‰‹•ƒ‡’‹”‹ - cal question I cannot address here. 7 Primljeno: 27. novembra 2013. Prihvaćeno: 7. decembra 2013.

References ƒ Š‹ŽŽ‡”ǡǤǡƒ ‹ƒ•ǡǤǡ—„‘—Ž‡ǡǤƒ†‘”ƒ–ƒǡ Ǥǡͥͥ͝͠ǡDz‘•‡”˜ƒ–‹‘‘ˆƒ ˆ— –‹‘ƒŽŠ‹‡”ƒ” Š›„‡–™‡‡ƒƒŽ‹ƒƒ†‹•‡ – ‘šȀ ‰‡‡•ǡdz EMBO J. ͟͝ǣͥ͟͜͝Ǧͥ͝͠͝Ǥ ƒ–‡•‘ǡǤǡͤͥ͝͞ǡDz—‡”‹ ƒŽ˜ƒ”‹ƒ–‹‘‹–‡‡–Šǡ™‹–Šƒ†‹• —••‹‘‘ˆ–Š‡ conception of homology,” Proc. Zool. Soc. Lond. ͤͥ͝͞ǣ͜͝͞Ǧ͝͝͡Ǥ ¡ ŠŽ‡”ǡ ƒ†‡–‡”ǡǤ͜͜͜͞ǡDz‡ŽŽ’‘Žƒ”‹–›‹›‡ƒ•–ǡdz”—„‹ǡǤǡ‡†Ǥǡ Cell polarity . ”ƒ†‘ǡǤǤƒ†‹ŒŠ‘—–ǡ Ǥ Ǥǡͣ͜͜͞ǡDzŠ‡’‹”‹ ƒŽ‘‡“—‹˜ƒŽ‡ ‡‘ˆ ‡‹ ƒ† ‡‘–›’‹ ‘†‡Ž•‘ˆ‡Ž‡ –‹‘ǣȋ‡ ‹•‹˜‡Ȍ‡ˆ—–ƒ–‹‘‘ˆ ‡‹ ‡Ž‡ –‹‘‹•ƒ†Ž—”ƒŽ‹•–‹  ‡‹ ‡Ž‡ –‹‘‹•ǡdz Philosophy of Science ͣ͟ȋ͟Ȍǣͣͣ͞Ǧͥͤ͞Ǥ ”ƒ†–•ǡǤǤǤƒ†‘–ƒˆ—”‘ǡ Ǥǡͥͥͣ͝ǡDz‡ –‘” ‹‡Ž†‘†‡Ž•‘ˆ ‘”’Š‘‰‡•‹•ǡdz—•†‡ǡǤ Ǥǡ”ƒ†–•ǡǤǤƒ†”ƒ‹‘”ǡǤǤ Ǥǡ‡†•Ǥǡ Physical Theory in Biology ( Studies of Nonlinear Phenomena in Life Sciences – Vol. 4), ‘”Ž† ‹‡–‹Ƥ Ǥ

7 A somewhat cynical way of directing an attempt to answer such a question would „‡ƒ•—‰‰‡•–‹‘–‘Ƥ†‘—––Š‡‡š–‡–‘ˆ–Š‡”‡•‘—” ‡•ƒ†”‡•‡ƒ” Š–‹‡ƒŽŽ‘ ƒ–‡† to the study of inheritance in ciliates and how it fares in comparison to “normal- • ‹‡ ‡dz’”‘Œ‡ –•™‹–Š‹–Š‡‘†‡”›–Š‡•‹•’ƒ”ƒ†‹‰Ǥ –‹‰Š––—”‘—––Šƒ–ƒ› - ƒ”†‹–Šǯ•™ƒ”‹‰‹‰Š–„‡ —””‡–Ž›Œ—•–‹Ƥ‡†‡˜‡‘”‡–Šƒ™Š‡‘”‹‰‹ƒŽŽ› voiced, in the case of those embracing the pragmatic attitude as well. SLOBODAN P EROVIĆ THE REBIRTH OF THE MORPHOGENETIC FIELD

”ƒ†–•ǡǤǤǤƒ†”ƒ‹‘”ǡǤǤ Ǥǡͥͥ͜͝ǡDz‘ǦŽ‹‡ƒ”Ƥ‡Ž†‘†‡Ž‘ˆ patter formation: interaction in morphallactic regulation,” Journal of Theoretical Biology ͢͝͠ǣͣ͟Ǧ͢͡Ǥ ”ƒ›ǡǤǡ͜͜͞͝ǡ Cell Movements: From Molecules to Motility ǡ‡™‘”ǣƒ›Ž‘”Ƭ ”ƒ ‹•‰”‘—’ǡ ƒ”Žƒ†—„Ž‹•Š‹‰Ǥ ”‹‰ƒ†–ǡ ǡͣ͜͜͞ǡDz›’‘Ž‘‰›‘™ǣŠ‘‘Ž‘‰›ƒ††‡˜‡Ž‘’‡–ƒŽ ‘•–”ƒ‹–• explain evolvability,” Biology and Philosophy ǡ͞͞ȋ͡Ȍǣ ͣͥ͜Ǧͣ͞͡ ŠƒŽ‡”ǡǤǤƒ†ƒ‘ǡǤǤǡͥͥ͢͝ǡDz‘Ǧ‡†‡Ž‹ƒǡŠ‡”‹–ƒ„Ž‡„Ž‘ •–‘ DNA rearrangement are induced by loading the somatic nucleus of ‡–”ƒŠ›‡ƒ–Š‡”‘’‹Žƒ™‹–Š‰‡”Ž‹‡ǦŽ‹‹–‡†ǡdz‘ŽǤ‡ŽŽǤ‹‘ŽǤ ͢͝ǣͤ͟͢͡Ǧͣ͟͢͢Ǥ ƒ™‹•ǡǤǡͥͤ͝͞ǡ The extended Phenotype ǡšˆ‘”†ǣǤ Ǥ ”‡‡ƒǤ Dawkins, R., 1995, River out of Eden: A Darwinian View of Life ǡ‡™‘”ǣƒ•‹  ‘‘•Ǥ ‡ŽŽƒ–”‡ǡǤǡƒƒ”†ǡǤƒ† ڐ ›ǡǤǡ͜͜͢͞ǡDz‡“—‡–‹ƒŽ”‘–‡‹‡ ”—‹–‡– in C. elegans Centriole Formation,” Current Biology ͢͝ǣͤ͝͠͠Ǧͤͥ͝͠Ǥ ”—„‹ǡǤǡ‡†Ǥǡ͜͜͜͞ǡ Cell polarity ǡšˆ‘”†‹˜‡”•‹–›”‡••Ǥ ”ƒ‡Žǡ Ǥǡͥͤ͝͞ǡDz Ž‘„ƒŽ’ƒ––‡”‹‰‹•‹‰Ž‡ ‡ŽŽ•ǡdz ‘—”ƒŽ‘ˆŠ‡‘”‡–‹ ƒŽ 196 ‹‘Ž‘‰›ͥͥǣͥ͝͝Ǧ͟͝͠Ǥ Frankel, J., 1989, Pattern Formation: Ciliate Studies and Models , Oxford: šˆ‘”†‹˜‡”•‹–›”‡••Ǥ ”ƒ‡Žǡ Ǥǡͥͥ͝͝ǡDzŠ‡ƒ––‡”‹‰‘ˆ‹Ž‹ƒ–‡•ǡdz J. Protozool. ͤ͟ȋ͡Ȍǡͥ͡͝Ǧ͡͞͡Ǥ ”ƒ‡Žǡ Ǥǡ͜͜͜͞ǡDz‡ŽŽ‘Žƒ”‹–›‹ ‹Ž‹ƒ–‡•ǡdz”—„‹ǡǤǡ‡†Ǥǡ Cell polarity ǡͣͤǦ͜͝͡Ǥ ‹Ž„‡”–Ǥ Ǥǡ’‹–œ ǤǤƒ†ƒˆ–ǤǤǡͥͥ͢͝ǡDz‡•›–Š‡•‹œ‹‰˜‘Ž—–‹‘ƒ”› ƒ†‡˜‡Ž‘’‡–ƒŽ‹‘Ž‘‰›ǡdz Developmental Biology ͣ͟͝ǣͣ͟͡Ǧͣ͟͞Ǥ ‘†ˆ”‡›Ǧ‹–ŠǡǤǡ͜͜͜͞ǡDzš’Žƒƒ–‘”››‡–”‹‡•ǡ”‡ˆ‘”ƒ–‹‘ǡƒ† Developmental Theory,” Philosophy of Science ‘ŽǤͣ͢ǡ”‘ ‡‡†‹‰•ǡ ͟͞͞Ǧ͟͟͝Ǥ ‘Ž†• Š‹†–ǡǤǤǡͥ͟͝͡ǡ ‡Ǥ†—••‡‡‹‰‡• Šƒˆ–ȋ–‡”•— Š—‰‡ƒ ”‘•‘’Š‹Žƒ ǡ Ȍ‹‡–•Ǥ †—–Ǥ„•–ǤǤ‡”‡”„Ǥͥ͢ǣͤ͟Ǧ͟͝͝Ǥ ‘‘†™‹Ǥǡͥͤ͝͠ǡDz‡Žƒ–‹‘ƒŽ‘” ‹‡Ž†Š‡‘”›‘ˆ‡’”‘†— –‹‘ƒ† –• ˜‘Ž—–‹‘ƒ”› ’Ž‹ ƒ–‹‘•ǡdz‹ ‘Ǥǡ‡†Ǥǡ Beyond Neo-Darwinism: An Introduction to the New Evolutionary Paradigm ǡ‘†‘ǣ ƒ†‡‹  ”‡••ǡͥ͞͝Ǧ͞͠͝Ǥ ‘‘†™‹ǡǤǤƒ†”ƒ‹‘”ǡǤǤ Ǥǡͥͤ͝͡ǡDz‹’ƒ†™Š‘”Ž‘”’Š‘‰‡‡•‹•‹ Acetabularia „› ƒŽ ‹—Ǧ”‡‰—Žƒ–‡†•–”ƒ‹Ƥ‡Ž†•ǡdz Journal of Theoretical Biology ͣ͝͝ǣͣͥǦ͜͢͝Ǥ ”‹ƥ–Š•ǡǤǤǡͣ͜͜͞ǡDzŠ‡’Š‡‘‡‘‘ˆ ‘‘Ž‘‰›ǡdz Biology and Philosophy ͞͞ȋ͡Ȍǣ͢͟͠Ǧͤ͢͡Ǥ Œ‡ŽǡǤǤǡͥͤ͢͝ǡDz •‘Ǧ ‡‹  Š‡”‹–ƒ ‡ ˜‘Ž˜‡†‹ƒ” ‹‘‰‡‡•‹•ǫ ›–‘–ƒ –‹ ‘†‡Ž‘ˆ”ƒ•ˆ‘”ƒ–‹‘ǡdz Journal of Theoretical Biology 119: ͤͥǦ͜͝͝Ǥ ƒ„Ž‘ƒǡǤǡ͜͜͞͡ǡ˜‘Ž—–‹‘‹ˆ‘—”†‹‡•‹‘•ǣ‰‡‡–‹ ǡ‡’‹‰‡‡–‹ ǡ behavioural, and symbolic variation in history of life, Cambridge: ƒ„”‹†‰‡‹˜‡”•‹–›”‡••Ǥ Jablonka, E. and Szathmáry, E., 1995, “The evolution of information storage and heredity,” Trends in Ecology and Evolution ͜͝ǣ͜͢͞Ǧ͞͝͝Ǥ ‡ŽŽ‡”ǡǤ Ǥǡ͜͜͜͞ǡ The Century of Gene ǡƒ„”‹†‰‡ǣƒ„”‹†‰‡‹˜‡”•‹–›”‡••Ǥ ”‡‹•ǡǤƒ†ƒŽ‡ǡǤǡͥͥͥ͝ǡ Guidebook to the Cytoskeletal and Motor Proteins , ǣšˆ‘”†‹˜‡”•‹–›”‡••Ǥ THE NOTION AND STRUCTURE OF EXPLANATION IN THE NATURAL AND SOCIAL SCIENCES

”—Žƒ—ˆǡǤǡͥͥ͟͝ǡDz ‘š‰‡‡•ƒ†’ƒ––‡”ˆ‘”ƒ–‹‘‹–Š‡„”ƒ Š‹ƒŽ”‡‰‹‘ of the vertebrate head,” Trends Genet. ͥǣ͜͢͝Ǧ͝͝͞Ǥ ƒ†ƒǡǤǤǡͥͥ͝͝ǡDzŠ‡ Š‡”‹–ƒ ‡‘ˆ “—‹”‡†Šƒ”ƒ –‡”‹•‹–‹ •ǡdz Annual Review of Genetics ͞͡ǣ͝Ǧ͜͞Ǥ ™‘ơǡǤǡͥͥ͜͝ǡDzǯ‘”‰ƒ‹•ƒ–‹‘†— ‘”–‡š Š‡œŽ‡• ‹Ž‹±•ǣ—‡š‡’Ž‡†ǯŠ±”‡†‹–± de caractère acquis,” Comptes rendus de l’Académies des Sciences Paris ͟͜͝ǣͥ͜͝Ǧ͝͝͝Ǥ ƒŽ‹ ‹ǡ Ǥǡ‹ƒ‡––‹ǡǤǤǡ‡• ŠŽ‡ǡǤƒ† ‹‹•ǡǤǡͥͥ͝͞ǡDz —ƒ ͠ ”‡‰—Žƒ–‘”›‡Ž‡‡–’”‘˜‹†‡•Š‡ƒ†Ǧ•’‡ ‹Ƥ ‡š’”‡••‹‘‹ Drosophila embryos,” Nature ͤ͟͡ǣ͟͠͡Ǧͣ͟͠Ǥ ƒ›ƒ”†‹–Šǡ Ǥǡͥͤ͟͝ǡDz˜‘Ž—–‹‘ƒ†‡˜‡Ž‘’‡–ǡdz ‘‘†™‹ǡǤǤǡ ‘Ž†‡”ǡ N. and Wylie, C.C., eds., Development and Evolution , Cambridge: ƒ„”‹†‰‡‹˜‡”•‹–›”‡••ǡ͟͟Ǧ͠͡Ǥ  ‹‹•ǡǡ—œ‹‘”ƒǡǤǤƒ† ‹‹•ǡǤǡͥͥ͜͝ǡDz —ƒ Hox ͠Ǥ͞ and Drosophila ‡ˆ‘”‡†‡ ‘†‡•‹‹Žƒ””‡‰—Žƒ–‘”›•’‡ ‹Ƥ ‹–‹‡•‹ Drosophila embryos and larvae,” Cell ͢͟ǣͥͥ͢Ǧͥͣ͢Ǥ  ‹‹•ǡǤƒ†”—Žƒ—ˆǡǤǡͥͥ͝͞ǡDz ‘‡‘„‘š‰‡‡•ƒ†ƒš‹ƒŽ’ƒ––‡”‹‰ǡdz Cell ͤ͢ǣͤ͟͞Ǧ͟͜͞Ǥ ‹ Š‘†ǡǤǤǡͥͤ͝͝ǡDz‘•‹–‹˜‡ ‡—”‹•–‹ •‹˜‘Ž—–‹‘ƒ”›‹‘Ž‘‰›ǡdz The British 197 Journal for the Philosophy of Science ͟͞ǡ͝Ǧ͟͢Ǥ òŽŽ‡”ǡ ǤǤƒ†‡™ƒǡǤǤǡ͜͜͟͞ǡDz”‹‰‹ƒ–‹‘‘ˆ”‰ƒ‹•ƒŽ ‘”ǣŠ‡ ‘”‰‘––‡ƒ—•‡‹˜‘Ž—–‹‘ƒ”›Š‡‘”›ǡdzòŽŽ‡”ǡ ǤǤƒ†‡™ƒǡ S.A., eds., Origination of Organismal Form ǡŠ‡ ”‡••Ǥ ƒ‡›ǡǤǤǡͥͤ͝͠ǡDz‡˜‹‡™‘ˆ ‘‘†™‹ǡǤǤǡ ‘Ž†‡”ǡǤƒ†›Ž‹‡ǡǤǤǡ‡†•Ǥǡ Development and Evolution ,” Journal of Protozoology ͟͝ǣ͟͢͡Ǥ ‘™ƒ ‹ǡǤǡ‹Œƒ›ƒǡǤǡŠ‘—ǡǤǡ Š‘–ƒ—•ǡǤǡ‘ƒǡǤƒ†ƒ†™‡„‡”ǡ Ǥ Ǥǡͣ͜͜͞ǡDzǦ‡†‹ƒ–‡†‡’‹‰‡‡–‹ ’”‘‰”ƒ‹‰‘ˆƒ‰‡‘‡ rearrangement pathway,” Nature †‘‹ǣ͜͝Ǥͤ͜͟͝Ǥ ›ƒƒǡǤǡ͜͜͜͞ǡ The Ontogeny of Information: Developmental Systems and Evolution ǡ͞†‡†Ǥǡ—”Šƒǣ—‡‹˜‡”•‹–›”‡••Ǥ ‡ŽŽ‡–‹‡”ǡǤǡǯ‘‘Ž‡ǡǤǡ Š™ƒ‰‡”ǡǤǡ ›ƒǡǤǤƒ†òŽŽ‡”Ǧ‡‹ Š‡”–ǡǤǡ ͜͜͢͞ǡDz‡–”‹‘Ž‡ƒ••‡„Ž›‹ Caenorhabditis elegans ,” Nature ͠͠͠ǣͥ͢͝Ǧ͟͞Ǥ Rose, S., Lifelines: Biology Beyond Determinism ǡšˆ‘”†ǣšˆ‘”†‹˜‡”•‹–› ”‡••Ǥ ‘‡„‘”ǡǤǤǡͥ͢͟͝ǡDz‘‡•’”‡ˆ‘”‡† ‡ŽŽ•–”— –—”‡’Žƒ›ƒ‡••‡–‹ƒŽ”‘Ž‡‹ ‡ŽŽŠ‡”‡†‹–›ǫdzǡŽŽ‡ǡ ǤǤǡ‡†ǤǡŠ‡ƒ–—”‡‘ˆ‹‘Ž‘‰‹ ƒŽ‹˜‡”•‹–›ǡ‡™ ‘”ǣ ”ƒ™Ǧ ‹ŽŽǡ͢͝͡Ǧ͞͞͝Ǥ ‘‡„‘”ǡǤǤǡDz ‡‡ƒ –‹‘‹†‡˜‡Ž‘’‡–ǡdz Proc. Roy. Soc. Lond. ͣ͢͝ǣ ͣ͟͠Ǧ͟͢͢Ǥ –‡–ǡ Ǥǡͥͤ͝͞ǡDzŠƒ–‹•ƒ’”‘‰”ƒǫdzǡ Evolution and Development, Dahlem Workshop Report ǡ‡”Ž‹ǣǦ’”‹‰‡”‡”Žƒ‰ǡ͞͞ǣ͝͝͝Ǧ͟͝͝ Thompson, E., Mind in Life ǡšˆ‘”†ǣšˆ‘”†‹˜‡”•‹–›”‡••Ǥ ƒŽ‡ǡǤǤƒ†‘•ƒ™ƒǡ Ǥͥͥ͜͝ǡDz”‘–‡‹‘–‘”•ƒ†ƒš™‡ŽŽǯ•†‡‘•ǣ†‘‡• the mechanochemical transduction involve a thermal ratchet?”, Adv. Biophys. ͢͞ǣͥͣǦ͟͝͠Ǥ ‡„•–‡” Ǥƒ† ‘‘†™‹Ǥǡͥͤ͝͞ǡDzŠ‡”‹‰‹‘ˆ’‡ ‹‡•ǣ–”— –—”ƒŽ‹•– Approach,” Journal of Social and Biological Structures ͡ǣ͝͡Ǧͣ͠Ǥ SLOBODAN P EROVIĆ THE REBIRTH OF THE MORPHOGENETIC FIELD

Slobodan Perović Oživljavanje koncepta morfogenetskog polja u objašnjenjima u biologiji Sažetak ƒœƒ–”ƒ†˜‡—’‘–”‡„‡‘ ‡’–ƒ‘”ˆ‘‰‡‡–•‘‰’‘ŽŒƒǡ‘Œ‹Œ‡Ƥ‰—”‹”ƒ‘ —„‹‘Ž‘‰‹Œ‹ͥ͝Ǥ˜‡ƒ‘–‹˜‹•ƒ•’‡ ‹Ƥ«‹‘–‘Ž‘捋’”‹•–—’‹ƒ–‘‰˜”‡ - ‡ƒǡ ‘Œ‹•‡ ƒ‘˜‘’‘Œƒ˜ŽŒ—Œ‡ ‹•˜‡ Œ‡”‡Ž‡˜ƒ–‹Œ‹—‘„ŒƒæŒ‡Œ‹ƒ ‹ - ”‘„‹‘Ž‘捋Š ˆ‡‘‡ƒǤ ƒ‘¯‡ ”ƒœƒ–”ƒ ‘†‘• ‘˜‹Š —’‘–”‡„ƒ ’”‡ƒ Ǯ‡–”ƒŽ‘Œ†‘‰‹ǯ‘†‡”‡„‹‘Ž‘‰‹Œ‡ǡƒ‘‹’”‡ƒ‘†‡”‘Œ•‹–‡œ‡ƒ” - vinizma i moderne genetike. Tzv. indukovano morfogenetsko polje je re- œ—Ž–ƒ–‘†”‡¯‡‹ŠƤœ‹«‹Š•‹Žƒȋ’”Ǥ‰”ƒ˜‹–ƒ ‹‘‘‰’‘ŽŒƒȌǡ‹Ž‹•–‡«‹ŠƤœ‹«‹Š ƒ”ƒ–‡”‹•–‹ƒȋ’”Ǥ˜‹•‘œ‘Ǧ‡Žƒ•–‹«‘‰Ȍ’‘ŽŒƒǤƒ˜‘‘”ˆ‘‰‡‡–•‘’‘ŽŒ‡ ’”‡†•–ƒ˜ŽŒƒ•ƒ‘•Žƒ„‹œƒœ‘˜‡–”ƒŽ‘Œ†‘‰ƒ‹‘†‡”‘Œ•‹–‡œ‹–‹‡斑 ‹†‹”‡–‘ǡ‹ƒ‘œƒ«ƒŒ‘ǡ‘‰”ƒ‹«ƒ˜ƒ˜ƒ”‹Œƒ„‹Ž‘•–ƒ‘Ž‡—Žƒ”‘‹ - ˜‘—Ǥƒ‘–‘‰ƒ•‡ˆ‘—•‹”ƒƒ‘„ŒƒæŒ‡Œƒ‘Œƒ—˜‘†‡•–”—–—”ƒŽ‘ƒ - sledjivanje u ciliatnim protozoama, kao i na eksperimentalnu evidenciju ƒ‘Œ‹ƒ•‡œƒ•‹˜ƒ‘˜ƒƒ˜’”‹•–—’Ǥ Ž‘„ƒŽ‘©‡Ž‹Œ•‘‘”ˆ‘‰‡‡–•‘’‘ŽŒ‡ Œ‡Œ‡†‹‹ ƒ–ƒ˜‘‰ƒ•Ž‡¯ƒǤ‹•—–—Œ‡”‡Ž‡˜ƒ–‡•Ž—«ƒŒ‡˜‡•–”—–—”ƒŽ‘‰ 198 ƒ•Ž‡¯ƒ— ‹Ž‹ƒ–‹ƒ‘Œ‡†‘˜‘†‹†‘——–”ƒæŒ‹Šǡƒ‘‹ˆ— ‹‘ƒŽ‹Š’”‘‡ - ƒ‹‹•–‹«‡†ƒ‹Œ‡’”‹•—–ƒ—‘”–‡•—ǡ‹–‹†ƒ‹ƒ‘–”‘Ž—ǡƒ Ž‘ƒŽ‘‹Ž‹‰Ž‘„ƒŽ‘‹˜‘—’‘ŽŒƒǤƒœƒŒƒ‘’‘œƒ–‹Ƥœ‹«‹’‘ŽŒ‹ - ƒ‘‰——ƒ’”‡†‹–‹–ƒ˜ƒ‘„ŒƒæŒ‡Œƒ‹”ƒœ—‡˜ƒŒ‡‘”ˆ‘‰‡‡–•‘‰’‘ - ŽŒƒƒ‘Œ‡†‹‹ ‡”ƒœ˜‘Œƒ‹ƒ•Ž‡¯‹˜ƒŒƒǤ Ključne reči: „ŒƒæŒ‡Œ‡Ǣ„‹‘Ž‘‰‹ŒƒǢ‘”ˆ‘‰‡‡–•‘’‘ŽŒ‡Ǣ‘†‡”ƒ•‹–‡ - za u biologiji