3 98 



Biogen in the Ovarian Egg. 



As to the relation of the biogen liquid to the germinative vesi- 

 cle, and which of them first appears, I could not satisfy myself 

 neither in (he eggs of Ascidia nor in those of the other Mollnsks 

 and Worms which I have hitherto examined. Although in some 

 instances I thought I had found an ovulum consisting of a simple 

 cell, yet on examination with a higher power, I commonly de- 

 tected the enclosed germinative vesicle. My friend, Professor 

 Gilman of New York, who has made extensive investigations of 

 the ovarian egg of fishes, maintains on the contrary, that in the 

 ovarian egg of the perch, the outer (yolk) membrane appears first, 

 and that even the separation of the yolk, under the form of a 

 slight cloud, precedes the formation of the germinative vesicle.* 



It is doubtful therefore, whether a law is discoverable which 

 shall be applicable in this respect to the whole animal kingdom. 



facts observed in a marine Worm, 



Mea 



the 



following 



or 



(Sigalion,) may not be without interest. 



Last spring 1 had several times an opportunity of examinin 

 ovarian eggs of the Sigalion. I found them, as usual in Annelids, 

 collected on each side of the intestinal canal. The eggs were 

 nearly mature, and the yolk opaque. But I was struck by a red- 

 dish spot in each egg, except the very smallest ; (figs. 10-14; the 



10. 



11. 



12. 



18. 



14. 





Z^ 



,■ 







'4 



■ 





Ovarian egg* of the, Sigalion, magnified 40 times, f 



red spot is here distinguished by lined shading). What was my 

 astonishment on bringing them under the compressorium, to see 

 that this red spot was enclosed in a transparent vesicle ; in other 

 words, that it was the germinative dot (t* ula WagTteH)! 

 Besides this, I observed that in many eggs, particularly the larger 

 ones, the red germinative dot itself enclosed a clear transparent 

 vesicle, as I had seen it in the eggs of Actinia, and as Valentin 

 has observed it in the ovarian egg of the Echini, and which I 

 for that reason propose to call Vesicula Valentin i. 



Whatever may be the office assigned to each of these parts of 

 the eg , thus much clearly follows from this obsen ttion, that 

 from the beginning there must be a definite arid essential distinc- 

 tion in their composition. And it seems to me that this decided 



* He also maintains the existence of a double covering in the egg of fishes,— -a 

 yolk-membrane and a shell-membrane, neither of them destitute of structure. 

 f Fig. 10. A very small egg without germinative dot. 

 Fig. 11, The red germinative dot appear* 



Fig. 12. The red germinative dot lias grown larger. ^ . .. 



Fig. 13. There i< seen in the germinative dot a si 11 clear cell, (Vesicula Valentini.) 

 Fig. 14. The vesicula Valentini is very distinct. 



/ 



