330 M. A. Schneider's Contributions to the 



So that if it be considered possible that contractile spaces may 

 occur in a primordial vesicle without the necessity for a peculiar 

 apparatus of contractile fibres, Polytoma fulfils all the requisite 

 conditions of a cell. 



That Polytoma is an animal may be maintained upon two 

 grounds. 



1. The constitution of the investing membrane. — As soon as the 

 starch-like granules have been destroyed by the long action of 

 concentrated sulphuric acid, no part of the creature is coloured 

 blue by iodine. Now we have no more reason for believing that 

 the vegetable cell-membrane must necessarily consist of cellulose, 

 than that the animal cell-membrane should not consist of that 

 substance, so that we are still compelled to seek for other cha- 

 racters for their distinction. These would be — 



2. The contractile spaces. — A statement of Cohn's * has cer- 

 tainly rendered it doubtful, whether the occurrence of these is 

 henceforward to be regarded as an essential indication of an ani- 

 mal nature. He says, " On the other hand, certain genera of 

 Algse exhibit a stage of development, in which, in external form, 

 in the absence of a cellulose membrane, in the distinct existence 

 of ciliary organs of motion, red eye-like spots, vacuoles, and, 

 according to a very recent discovery, of internal pulsating 

 spaces, they undoubtedly appear very similar to the Asto- 

 matous Infusoria/' If these pulsating spaces occur only 

 in unicellular Algse provided with cilia, these perhaps should 

 properly be restored to their place amongst animals, notwith- 

 standing the subsequent appearance of cellulose-membrane upon 

 them. But if they occur in the swarm-cells of the Conferva?, 

 they certainly cease to be a characteristic of animal nature. 

 Thus, if we are not yet in a position to refer Polytoma with per- 

 fect certainty to its proper place, there is decidedly no reason for 

 excluding it from the animal kingdom. We will not, however, 

 venture to consider the Infusoria furnished with a mouth (Sto- 

 matoda, Von Siebold), as formed, like Polytoma, upon the type of 

 a simple cell ; for, high as we may rate the advantage accruing to 

 science from the comparison of the Protozoa with simple cells, 

 difficulties stand in the way of its complete application in the 

 case of animals of such complicated structure as the Vorticellce 

 for example ; and these cannot be considered as entirely done away 

 with, until the history of their development has furnished proof 

 that at no period does a fusion of several cells take place. 



In conclusion we bring together the results of the investiga- 

 tion as shortly as possible. 



* Zwanzigster Jahresbericht dfer sehlesischen Gesellschaft fur vater- 

 laudische Cultur, 1852, p. 46. 



