80 



estate of Dr. Burnett, reported that the purchase had been 

 made at a cost exceeding, by ten dollars, the sum appropri- 

 ated. The report was accepted, and the purchase ratified. 

 Dr. Durkee exhibited the collection to the Society, and was 

 requested to take charge of it. 



September 20, 1854. 



The President in the Chair. 



Prof. Jeffries Wyman gave an account of some observa- 

 tions on the development of Anableps Gronovii, a vivipa- 

 rous fish from Surinam. 



He described the external conditions of development of fishes 

 in general, as manifest in the oviparous and viviparous species. 

 The latter are divided into two groups ; the first including 

 those species in which the egg enters the oviduct before the 

 development of the embryo begins ; the second includes all such 

 as have a gestation almost wholly ovarian. In the former group 

 are found Spinax, Carcharias, Torpedo and other Plagiostomes ; 

 in the second, Anableps, Poecilia, Blennius, and Embiotoca. 

 Prof. Wyman had examined the ovarian eggs of Anableps, and 

 found them surrounded, after they had acquired a certain size, 

 by a transparent space limited by thickened stroma which formed 

 a distinct closed sac. The egg was free in this sac, as the mam- 

 miferous ovum is in the Graafian vesicle. 



The youngest embryos examined were less than four fifths of 

 an inch in length, and had the yelk-bag attached ; this last was 

 covered with papillae, arranged in a linear series, but which were 

 not vascular as stated by Valenciennes. Another series of 

 foetuses were more than an inch in length, and resembled the 

 preceding, except that the eye had begun to assume the pecu- 

 liarity of the adult, viz., the dumb-bell-shaped pupil. 



