620 William Patten 



or ideas, and indeed has failed to see wliat was so clearly poiuted out 

 for him in the much earlier work of Babuchin. In some inexplicable 

 manner, he has attributed the omnipresent »Plättchenstructur« to the 

 b odi es of the colorless cells, while he has entìrely overlooked the rods 

 themselves. 



Fkaisse (36) considered that the colorless cells from the eyes of 

 Patella and Fissurella (he failed to recognize theni in Haliotìs) act as 

 Supports for the pigmented cells ; he also sees in them the organs which 

 scerete the vitreous body and leus. This idea has taken firm root in the 

 minds of subsequent authors, who bave compared them with the gland 

 cells found generally distributed in the Molluscan hypodermis. More 

 recently, hoAvever, Hilger (40) has recognized that they play an impor- 

 tant part in the formatiou of the rods. 



That the colorless cells are something more than mere gland cells 

 is sufficiently proved bythe complex structure which I bave shown that 

 they possess, and the homology that may be pointed out between them 

 and cells which uudoubtedly play the most important roll in the more 

 highly developed eyes of Arca and Pecten. Fkaisse noticed the fibres 

 in the lens, as he called it, and although, at first, he is in doubt whether 

 to cali them rods, he finally concludes that, in ali probability, they are 

 artificially produced by the coagulation of the lens. He believes, 

 moreover, that the lens is first secreted by the support cells, and after 

 it has gained a sufficient size the vitreous body is produced. It seems 

 to me that he has reversed the order, and that the lens is simply a part 

 of the vitreous body hardened by exposure to the water, as in Haliotìs, 

 or by coagulation, as in the closed eyes of Fissurella. 



I, however, agree with him in considering the lens and vitreous 

 body as cuticular structures, but cannot consider, as he do es, that they 

 are secreted by the colorless cells alone; the cuticular substance Is 

 rather a modification of the walls of both pigmented and colorless cells, 

 and shows various degrees of density and of vitality, according as it is 

 more or less intimately connected with the cells to which it owes its 

 origin. 



The »Stübcheuzellen« of Carrière are so named because they 

 contaiu a colorless axis surrounded by pigment ; the former he calls the 

 rod, and the pigment cells, the rod cells, which he cousiders to be uu- 

 doubtedly the essential Clements of the retina. He adopts Fraisses 

 terminology, and considers with him that the colorless cells are scerete 

 cells, homologous with those large gland cells found in the general 

 hypodermis. The retinidial layer, he has overlooked, having confused 



