the Development of Anableps Gronovii. 439 



them one or two dark longitudinal lines were now visible ; 

 the general form of the body had assumed more precisely that 

 of the adult, and, as noticed by Valenciennes, the intestines 

 had obtained their permanent form. The external sexual 

 characters were not visible in any of the specimens examined, 

 though they were seen and figured in specimens of about the 

 the same size by Valenciennes. 



All of the foetuses of this female had escaped from their 

 original sacs, (no traces of which were now visible,) and were 

 all contained in one large cavity formed by the dilated ovary 

 which now had become analogous to an uterus, and extended 

 from the genital opening as far forwards as the bases of the 

 pectoral fins. The walls of this ovarian sac were sufficiently 

 thin to allow the foetuses to be seen through them ; on its 

 inner surface, as well as on that of some of the other speci- 

 mens, were to be seen numerous immature ova, some of them 

 microscopic and others as large as the sixteenth of an inch in 

 diameter. The coexistence of immature ova on the walls of 

 the ovarian cavity, with foetuses within it, corresponds with 

 what was noticed by Duvernoy in his investigations of the 

 embryology of Poecilia.* The more minute ovarian eggs, 

 though for a long time macerated in alcohol, yet preserved 

 their microscopic characters to a remarkable degree. The 

 smallest consisted of a cell, in the centre of which a nu- 

 cleus was visible, and around this last were a few granules 

 (Fig. 1) ; in the larger ova the granules have become more and 

 more abundant, and in some instances obscure the nucleus or 

 germ cell. After the egg has increased to a certain size, a 

 clear space (Figs. 2, 3 and 4) appears exterior to the vitel- 

 line membrane, which gradually increases to nearly twice the 

 diameter of the egg itself; this clear space is limited by the 

 substance of the stroma which becomes condensed around it, 

 and thus forms a distinct sac. If the ovum be compared to 

 that of a mammal, then the sac just described may be said 



* Annates des Sc. Naturelles. T. i. N. S. 1844. 



