n8 



BIOLOGICAL LECTURES. 



cell, while in Stentor a whole crown of such organs is formed 

 without any division into cells. Could one ask for a clearer 

 demonstration ? Are we not forced to conclude with Gruber 

 that " however great the difference between an infusorium and a 

 JiigJily organized animal, it cannot be a qualitative one. We 

 can assume tJiat tJie same vital elements serve in botJi as t/ie 

 foundation, only in ever neiv combinations. This kinsJiip 

 declares itself very clearly in the correspondence of many organs 

 of the infusoria with those of the higher organisms " (I.e. p. 16). 



FIG. 3. A, ''Corner cell" of Cyclas cornea. B, Section of three cells. 



letters as in Fig. 2. 



Other 



" So finden wir," says Gruber, " in einem Thiere, das 

 schon hoch auf der Stufenleiter der vielzelligen Organismen 

 steht, dieselben Grundelemente wieder wie in clem einzelligen 

 Infusionsthierchen. . . . 



" Wieder und wieder der Beweis von dem gottlich einfachen 

 aber auch gottlich gewaltigen Gesetze der Einhcit der Natnr" 

 (p. 1 8). 



The entoderm of Dicyema illustrates one or two points of interest in this 

 connection. We have here an organ in which, as often happens, in parasitic 

 degradation, cell-formation has been dispensed with. The entoderm remains 

 throughout life as a single cell, and the whole process of reproduction, for both 

 kinds of embryos, is carried on in the body of this cell without any cellular organs 

 whatever. 



In one respect this unicellular organ, which was undoubtedly once multicellular, 



