396 



Biogen in the Ovarian Egg. 



vesicles. The whole sphere, except the germinative vesicle, was 

 filled with them. In that of fig. 7, I found the yolk-granules or 



1. 



2. 



a 



4. 



5. 



6. 



<D 



i 



... 



1. 



a 



9. 



Ovarian eggs of the Aseidia rustics, magnified 100 times* 



vesicles much crowded, particularly in the middle, so that it was 

 with difficulty that I could distinguish the outlines of the germ- 

 inative vesicle. The granules had not only increased in number, 

 but it was also evident that a condensation had taken place in 

 them towards the middle, for it was only towards the edge that 

 the mass appeared loose. In the egg of fig. 8, the condensation 



had proceeded further. 



The germinative vesicle was no longer 



On the other hand 



visible,, except when I compressed the egg. 

 the vitelline mass seemed to withdraw itself more and more from 

 the edges, and already a wide border had appeared between the 

 outer membrane and the edge of the yolk. Finally I observed 

 in the ovary, several eggs of considerable size (fig. 9,) in whicli 

 the yolk formed a compact ball, well defined on all sides, and 

 surrounded by the transparent liquid as by an albumen, precisely 

 as it is in the eggs after they are laid.f 



From these observations it clearly appears, that this clear liquid 

 surrounding the yolk is quite different from the albumen of the 



eggs of higher animals. 



Far from being added from without, it 



seems to me on the contrary to be the fundamental substance, the 

 mother-liquid, from which the yolk is, as it were, precipitated. 



I 



* Kg, L Very small egg in which no germinative dot could be seen, but only the 

 germinative vesicle. 



I *. 2. A somewhat larger egg, with a small germinative dot. 



Fig. 3. A still larger egg, but yet entirely transparent 



Fig. 4. A light cloud is seen surrounding the genranairre vesicle. 



Fig. 5. Tli" cloud baa spread and \m more distinct, with a granular appearance. 



Fig. 6. The cloud tills the whole egg and appears d ttod i y as granular yolk buI ance. 



Fig. 7. The gnumW yolk wibst ice is dense* around the j rmroative vesicle. 



Fiir. 8. The gi >ular yolk eubstance begins to recede from the niar.L u The 

 germinative vesicle baa I »me quite indistinct. 



Fig. 9. The yolS mbitance i> condensed into a r* dar ball surrounded by a trans- 

 parent liquid, (the biogen.) The germinative vesicle is hidden. 



f Occasionally no formation of yolk takes place, and such eggs have been errone- 

 ously considered as empty shells. The biogen is present in these also, only unpro- 

 ductive. These eggs (the" supposed empty shells) occur particularly in the extremi- 

 ties of tke strings of eggs in Eolis, Doha, Acteon, &c. 



/ 



