87 



equal power in uniting the particles which make up a living 

 animal. 



As soon as the egg enters upon its organic life it begins 

 to revolve, and in this movement we have another coinci- 

 dence with the order of things in the formation of the plan- 

 etary system, according to the nebular hypothesis. 



With regard to Fishes, Mr. Desor remarked that it is not 

 yet certain that in their embryonic development they follow 

 exactly the process which has been observed in, the ova of 

 other animals. In the ovum of this class while yet in 

 the ovary, the yolk substance, containing a number of oil 

 drops, fills the whole space. When more developed it is 

 separated from the circumference of the ovum by a trans- 

 parent interval. It is a question yet undecided whether 

 there exists a true shell-membrane in these eggs, through 

 which water may have penetrated by endosmose, following 

 the condensing yolk. 



Here Mr. D. read a letter addressed to him by Prof. Gil- 

 man, of New York, confirming his observations, and coincid- 

 ing in his views with regard to the Biogen liquid, but going 

 even further than Mr. D. himself; and shewing that, by his 

 own researches, he had ascertained that even the germina- 

 tive vesicle is formed from it. He also expressed his belief 

 that a shell-membrane exists in the ovarian egg of most 

 Fishes, and that the liquid between it and the yolk-mem- 

 brane must have entered by endosmose. So that for the 

 present, the embryonic development of this class of animals 

 would seem to be an exception to the general rule. 



Mr. Ayres stated that he had recently been engaged in a 

 careful dissection of Catostomiis, to ascertain whether there 

 exists in this fish the curious arrangement of the muscular 

 apparatus of the pharyngeal bones, which he had demon- 

 strated in the genus Leuciscus. (See Proceedings, June 

 21st, 1848.) He had found that although the same muscles 

 exist in the throat of Catostomus as in Leuciscus, their 



