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 Pecilia.* 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 
Serm 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, 
thus forms a distinct sac. If the ovum be compared to 
that of a mammal, then the sac just described may be said 
* Annales des Sc. Naturelles. T. i. N. S. 1844. 
