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This article was downloaded by: [McGill University Library] On: 16 February 2015, At: 11:28 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Annals and Magazine of Natural History: Series 6 Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tnah12 XII.—The Mesozoon Salinella Johannes Frenzel Published online: 02 Oct 2009. To cite this article: Johannes Frenzel (1892) XII.—The Mesozoon Salinella, Annals and Magazine of Natural History: Series 6, 9:49, 79-84, DOI: 10.1080/00222939208677276 To link to this article: http://dx.doi.org/10.1080/00222939208677276 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. 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Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/ terms-and-conditions Downloaded by [McGill University Library] at 11:28 16 February 2015 M. J. Frenzel on the Mesozoon Salinella. 79 Tail longer than the head and body, brown above, pen- cilled with black terminally, orange-rufous on the sides and below. Palms and soles with the essential characters of those of G..qradlis, leucogaster, &c., i. e. naked, with five anterior and four posterior pads, but distinguished from all the species of this group by the fact that a band (about 4 millim, broad) of fine hairs passes across the soles at about the level of the base of the hallux. Skin of soles black. Skull very much as in G. !]rae{lis. Bulhe small, egg- shaped, their posterior part scarcely swollen. Teeth: upper incisors much bevelled~ each with one deep groove. Molars with the low, distinct, directly transverse lamime characteristic of this group of Gerbilles. Dimensions of the type (an adult specimen in skin) :- Head and body 140 millim. ; tail 155 ; hind foot 29. Skull : basal length 30 ; greatest length 35 ; tympanic breadth 16"5; nasals, length 14, breadth 3'7; interorbital breadth 6 ; interparietal, length 4, breadth 8"5 ; palate, length 18"5, diastcma 10, palatal tbramen 6"1 ; length of upper molar series 5"2 ; greatest diameter of halle 10'4 ; vertical height of brain-ease and bull~e combined 13"5. Hab. Wadelai. Type (87. 12. 1.50) collected and presented by Dr. Emin Pasha. A second specimen, collected at the same time and place, agrees in every respect with the type. These two specimens were presented to the Museum with Emin Pasha's first collection (see P. Z. S. 1888, p. 10, no. 24). Turning out now to be new, it is only just that they should receive the name of their distinguished discoverer. XlI.~The Mesozoon Salinella. By JOHANNES FRENZEL ~ Downloaded by [McGill University Library] at 11:28 16 February 2015 IT is a well-known fact that between unicellular and multi- cellular animals there hitherto stretched a gulf which was wider than that between the vegetable and animal kingdoms, for indeed the two latter, in spite of the advances which we have made in knowledge, are even to-day hardly separable from one another. The unicellular animals, usually com- prised under the name Protozoa, and embracing besides many doubtful forms of the Protista, not only consist, as their name * Translated from the ' Biologisches Centralblatt,' xi. Bd. no. I9 (October 15,1891), pp. 577-581. 80 M. J. Frenzel on the Mesozoon Saliuella. already implies, of a single cell which unites in itself all the various ihnctions of an animal organism, but also assume quite a peculiar position in many other respects, especially with regard to development. In the systematic arrangement of the group we are even obliged, hard though it will be for every modern zoologist, to allow ourselves to be swayed by p]*ysiological considerations, since here the purely morpho- logical and embryological foundations are insufficient ; and we are even ibrced to exclude them, at any ra~;e in general, fronl tt~iekel's fundamental principle of biogenesis, which is equally unsatisfactory. The multicellular animals, on the other hand, are not mere aggregates of cells, such as, moreover, are not unknown among the Protista, but they permit us to distinguish, albeit frequently with difi%ulty, a structure consisting of three la~ers, in that in the simplest case they possess an external layer of cells, which provides for sensory perceptions &c., next a median supporting tissue, and finally an internal one, which discharges the function of nutrition, since it clothes a cavity which is known as the gastral chamber, alimentary canal, &c. There is yet another by no means unimportant difference between unicellular and multicellular animals to which unfor- tunately far too little attention is paid, perhaps in conse- quence of the fact that it arises in the first plaee ti'om physio- logical conditions only. For if we disregard forms which exhibit holophytie nutri- tion, and therefore live like a lower form of plant, and further neglect the intestinal parasites, which in many cases, but not always, are able to absorb that which has already been digested by other animals, we find that the Protozoon cell receives its food into ¢tse~ digests it in its interior, and absorbs what is suitable. This is a so-called intra-cellular digestion, which in Metazoa, on the contrary, is only met with in isolated and exceptional eases ; for in the latter extra. cellular digestion prevails, which is accomplished on the principle of " one for all and all for one," since all the partici- Downloaded by [McGill University Library] at 11:28 16 February 2015 pating cells to a certain extent throw their digestive ferments into a common pot, in which digestion proceeds, exactly as cooking is done in a kitchen for a large number of persons. It follows that solid, in part absolutely indigestible bodies, are no longer taken up by the cells, as we found to be the case in Protozoa, but only fluid substanees in the shape of peptone, sugar, fat, &e. In consequence of this, those morphologi- cally specially constructed organs for the acquisition of food, such as we meet with in the Protozoa in the form of pseudo- podia, flagella, cilia, &e., are no longer necessary. We may ]VI. ft. Frenzel on tT~e Mesozoon Sallnella. 81 rather regard absorption in the Metazoa as a purely chemical process~ emanating from the living cells. Now~ should we desire to construct a multieellular animal from a number of Protozo% e.g. from Ciliate Infusori% we should consequently soon be confronted with a great physio- logical difficulty. We could indeed easily imitate the simplest ~Ietazoon typ% and so arrange the cells that they should surround a cavity possessing an incurrent opening. But how would nutrition proceed .9 The group of Protozoa would at all events obtain their food from the common cavity, but it would be directly introduced into the interior of the separate individuals~ there digested~ and so forth. It follows that in this construction of ours We should not get beyond a simple Protozoon colony~ and should still be a long way from obtaining a typical Metazoon. For although among the 1Vletazoa there are tbrms which possess intracel[ular digestion~ we must nevertheless not forget that it is only the endoderra cells which can be concerned therein. But yet all the other tissues must be similarly nourished, and this is effected by their receiving already digested matters from the intestinal cells. Were we able therefore still to regard the latter at all events as Protozoon cells~ this view would be absolutely inadmissible for the formeU the cells of the mesoderm and ectoderm~ and they must absorb in a manner similar to that of the intestinal cells which possess the power of extra- cellular digestion. From the foregoing considerations it is not difficult to see that the multi]amellar character of the Netazoa in itself entails the decisive difference which separates them fi'om the Proto- zo% and, further~ that the multicellular character~ as suetb is insufficient to bridge over the deep gulf between the two principal groups of the animal kingdom. It is well known that the title Mesozoa has already been bestowed upon organisms which it must be confessed are strange enough, and which rendered the justification of the term not improbable. But the position of the Orthonectids Downloaded by [McGill University Library] at 11:28 16 February 2015 and Dicyemids is nevertheless an extremely doubtful on% and points more to an affinity with the worms. The genus Triehoplax~ moreover~ has been with good reason assigned to the Metazoa by Fr. Schulze ; for although its conditions of nutrition may be regarded as being still very obscur% never- theless it has not been possible to determine that its digestive processes are intracellular.

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