The Journal of 

 Comparative Neurology and Psychology 



Volume XV 1905 Number 6 



SOME CELLULAR CHANGES IN THE PRIMARY 

 OPTIC VESICLES OF NECTURUS. 



By Clarence Loeb, A. M., M. D., 



S/. Lout's. 

 {From the Anatomical Laboratory , St. Louis University.) 



With Plate V. 



A superficial study of the optic vesicles as they develop in 

 Necturus showed certain interesting features, which have not 

 been heretofore described. On account of the large size of its 

 cellular elements, the cytological changes in this animal admit 

 of a more exact interpretation than is afforded by other verte- 

 brates. 



The formation of the neural plate in Necturus is initiated 

 by certain changes in tfcie ectodermal cells, which elongate from 

 the low cuboidal of the superficial ectoderm to the long colum- 

 nar type, as shown in Fig. \, e.c and n.c. The same changes 

 are shown under higher magnification in Figs. 7 and 8, Fig. 7 

 representing a cell near the center of the neural plate, and Fig. 

 8 an ectodermal cell beyond the margin of the neural plate. 



The cells of which Fig. 7 is a type are divisible into two 

 parts, a proximal and a distal. The former is full of yolk gran- 

 ules and usually contains the nucleus. This nucleus varies in 

 shape from round to long oval, its long diameter being from 

 two to three times the short. Sometimes it is irregular in 

 shape, in which case it is usually found near the center of the 

 neural plate. When the nucleus lies in the distal part of the 

 cell, it is frequently observed undergoing mitosis. 



