39 



snecies of -ledusac; the sizes of which range from ,024 tti'^. 

 to 1,5 -.im. Cun ina oro bosr.idea ha>ada^ the smallest a'ld 

 Polyxenia albescens the lartrest egg of the species included 

 in his lot. The egg of Turri1;o"sis is ,iust slightly than 

 that of Rathkea fasciculata according to the ■^easurcent of 

 i.;etschril:off . 



In the substance of the egg tv;c parts are distinguish- 

 able; an outer layer of cleareiY^ctoplasrr which consists 

 of viscid formative yolk conposed of protoplasm with veri 

 fine granules; and a central mass of e'^dorlas"' which is dense 

 and oraque end filled v/iih large, dark granules of nutri- 

 tive yolk. Fro- the fact thatfthe e-dorlasT is crowded with 

 these coarse dense granu^ies of nutritive naterial the egg 

 is very opaque and the ger-inal vesicle is not to be seen 

 frorr the exterior. Tlius the changes which take place dur- 

 ing maturation and fertilization, and the nuclear Phenom- 

 ena of segmentation, as well as the formation of the endo- 

 derm ca-Tiot be followed imhe living egg. For thislreason 



