DEVELOPMENTAL DYNAMICS 238:2357–2363, 2009 REVIEWS–A PEER REVIEWED FORUM Regeneration According to Spallanzani Panagiotis A. Tsonis* and Timothy P. Fox In this report, we elaborate on a letter that Spallanzani wrote to Bonnet reporting his findings on regeneration in worms, snails, tadpoles, and salamanders. The letter (original in French and translated in English; see Supplementary Material, which is available online) was written to discuss whether or not regeneration in these animals supports Bonnet’s theory on germs. The letter includes several drawings by Spallanzani, which were not published in the Prodromo, his book on Animal Reproduction. Spallanzani made important observations, which he described with considerable detail, but overall he was unable to confidently support Bonnet’s theory. This letter reflects the way of thinking in the 18th century that shaped the important scientific fields of regeneration and reproduction. Developmental Dynamics 238:2357–2363, 2009. © 2009 Wiley-Liss, Inc. Key words: Spallanzani; regeneration; animal reproduction Accepted 4 June 2009 INTRODUCTION of Creation. On the contrary, epigene- 1740 and on worm regeneration in sis allowed space for questioning the 1744 (Savioz, 1948; Dinsmore, 1991) Rooted in Aristotelian philosophy, the role of God. As expected when the first shocked the scientific world. Re´aumur belief that lower animals were gener- experiments in the 18th century re- and Bonnet were preformationists ated spontaneously from decay pre- vealed the regenerative power of ani- and, in fact, Re´aumur believed that vailed until the 17th century when mals, these two competing theories germs were contained within parts re- Redi in 1668 carried out well-con- trolled experiments that provided the were called upon to explain this new sponsible for regeneration. In his writ- property of animals. ings, Bonnet argued that Trembley’s first proof against it (Redi, 1668, th 1671). A similar view, epigenesis, de- The 18 century could very well be experiments with Hydra and his with veloped by Harvey, stated that new considered as the golden era in regen- worms supported the pre-existence of organisms appear from undifferenti- eration research. Many studies during germs and became a leading propo- ated matter. These ideas were sup- the previous century had led the way nent of the preformation theory. ported later in the 18th century by to understand how reproduction oc- Among these intellectual giants, Needhan and Buffon who believed curs and many theories and thoughts Lazzaro Spallanzani is also credited that organic molecules organized by were developed to explain how ani- as being one of the pioneers in regen- internal molds were responsible for mals (and humans) reproduce (Cobb, eration research. In 1768, Spallanzani animal generation (Benson, 1991). 2006). Naturally, scientists experi- published the Prodromo, his historical The rival position to epigenesis, which mented with regeneration in animals book on Animal Reproduction. At that prevailed at the end of the 17th cen- (which then was called actually repro- time, the word “reproduction” was tury, was preformation. According to duction). Pivotal discoveries by Re´au- used to denote “regeneration” as well. this, the organisms were preformed in mur on appendage regeneration in in- In his book, Spallanzani described the embryo. Preformation was also in sects in 1712 (Wheeler, 1926), by several types of regeneration with favor when it came to religious beliefs Tremblay on Hydra regeneration in mention of regeneration of the frog because it fit the notion that all gen- 1744 (Baker, 1952; Dawson, 1987), tail and salamander limbs. The ac- erations were established at the time and by Bonnet on parthenogenesis in counts were surprisingly quite short Additional Supporting Information may be found in the online version of this article. Department of Biology and Center for Tissue Regeneration and Engineering at Dayton, University of Dayton, Dayton, Ohio *Correspondence to: Panagiotis A. Tsonis, Department of Biology and Center for Tissue Regeneration and Engineering at Dayton, University of Dayton, Dayton, OH 45469-2320. E-mail: [email protected] DOI 10.1002/dvdy.22057 Published online 3 August 2009 in Wiley InterScience (www.interscience.wiley.com). © 2009 Wiley-Liss, Inc. 2358 TSONIS AND FOX Figs. 1–6. Anatomy and regeneration in worms. Fig. 1: The gross artery (red) attached to the intestines. Fig. 2: The artery branches into five vessels (red) as it reaches the head. Spallanzani describes the vessels as small bags composed of one or many constrictions. Fig. 3: The vein that runs from head to tail is winding. It is intersected by another vein, which is straightened. Fig. 4: The “boat” worm, a fresh water worm, whose tail is on the surface of the water (light blue), while the head is hidden in the mud (dark blue). Fig. 5: Regeneration in fresh water worm. A cone is produced. The reddish color at the base of the cone is the anus. Fig. 6: At the posterior part of the anus, a red line appears in the same direction as the artery of the animal (o). Spallanzani describes that at this stage he could not see circulation in the red line but later blood flows into the artery. with not much detail or any drawings sponded on September 14 and was nistic view of animal biology or how the that were common in publications of quite happy that Spallanzani shared issue of soul fits in a regenerating ani- that time. However, in a long letter to his views and that he was also work- mal). In addition, this letter also reflects Bonnet written on September 21, ing on earthworm regeneration. Bon- the clarity of thought that Spallanzani 1766, Spallanzani outlined in great net in a sense invited Spallanzani to possessed in order to explain his find- detail regeneration in many organ- pursue the work on earthworm regen- ings. We, therefore, strongly believe isms, including earthworm, snail, eration. An exchange of letters ensued that the contents of this letter should be frog, and salamander (Biagi, 1958; in which Spallanzani outlined a series of great historical value to scholars in Dinsmore, 1991). The letter, which of experiments that were inspired by developmental biology and regenera- reads as a research paper, is also dec- Bonnet’s influence. Bonnet mentioned tion research. Here we will highlight his orated with many drawings by Spal- that regeneration research should be major experiments and points. Also, we lanzani’s hand (original in French and able to resolve the germ concept, thus have reproduced the drawings and we translated in English can be found in inviting Spallanzani to elaborate on present them with added color as well. Supplementary Material). One of the this (Biagi, 1958; Dinsmore, 1991). The color is in accordance with the de- major reasons Spallanzani wrote this In his letter of September 21, Spal- scription that Spallanzani provides in letter was to discuss Bonnet’s theory lanzani casts doubts on the existence of on germs, according to which repro- germs for some types of regeneration his letter. Figures 1–17 have been set in duction and regeneration were medi- and obviously he does this with great the order in which they appear in the ated by germs that existed in the or- care not to offend Bonnet. Thus, this letter, but have been grouped according ganism. Spallanzani initiated letter bears enormous significance to the species. We will end this review correspondence with Bonnet on July about how scientists were thinking at by reflecting on how these ideas shaped th 18, 1765 by sending him copies of two that time and how they dealt with these scientific thought in the 18 century of his publications. On August 24, obstacles imposed by their social/reli- and how they relate to our thoughts in 1765, Spallanzani wrote again to Bon- gious status as well as by the prevailing the present day. Text in italics contains net critically commenting on Need- way of thinking of the time (for exam- comments by us related to Spallanza- ham and Buffon’s ideas. Bonnet re- ple, it questioned the Cartesian mecha- ni’s observations. REGENERATION ACCORDING TO SPALLANZANI 2359 REGENERATION IN ends of the head are dead but all the more or less equal parts. Almost all EARTHWORMS AND posterior parts containing the ovary the anterior parts regenerated (obvi- FRESHWATER WORMS and the small bags generated a head, ously these parts contained the repro- which in the end was equal to the orig- ductive system) while most of the pos- After a short salutation and com- inal one. terior parts (36/50) died. In the second ments on how some scientists view experiment, he cut the worm into three parts in a way that the anterior Bonnet’s research, Spallanzani sets Experiment 4 the stage by describing certain exper- part contained 3–6 rings and no re- iments he performed to learn about Divide longitudinally the body into productive system, and the middle the anatomy and physiology of the two parts from the head to two thirds part contained the reproductive sys- earthworm. Spallanzani provides of its length and then remove the pos- tem and the posterior part. At the end three drawings of the anatomy of ar- terior third (tail). Results: The two of the experiment, all the anterior teries and veins (Figs. 1–3). He then longitudinally divided parts and the parts were dead, the middle parts re- proceeds by outlining six different ex- tail part died. generated and many of the posterior periments to study regeneration in parts were alive but without signs of regeneration. Spallanzani also men- earthworm. Drawings outlining these Experiment 5 experiments and the results are tions that at the level of the tail, the shown in Supplementary Material. Divide the worm longitudinally into “boat” structure never failed to form, two parts from the tail to two thirds of and he also concludes that these Experiment 1 its length and then remove the ante- worms regenerate naturally because Transversal section of the earthworm rior part containing the head.