the Development of Anableps Gonovii. 435 
If. In the second group those fishes are comprised in which 
the gestation is either wholly or in part ovarian, the last 
Stages only of the process usually occurring in the oviduct. 
Among the genera included in this division are, Silurus,* Blen- 
nius,t Anableps,t Pecilia,§ and Embiotoca.|| In all of these 
genera impregnation takes placé@in the ovary, and, as seems 
probable, while the ovum is still invested with its original en- 
velopes. In Blenny, Rathké has shown, the ovarian gestation 
having continued about three weeks, that about the end of Sep- 
tember the sac ruptures, and that the embryo is discharged into 
the central cavity of the ovary, which is in fact the oviduct ; 
here the foetus remains till the beginning of January, when it 
is born. In Pcecilia the foetus is liberated and escapes into the 
oviduct towards the end of gestation. Valenciennes has given 
several details in relation to the development of Anableps Gro- 
novii, made for the most part upon specimens in an advanced 
Stage of fcetation, the smallest embryo being more than an 
inch long. He found only seven or eight foetuses in the so- 
called uterus of each female, and each of the young was sur- 
rounded by a distinct sac, which he regards as simply an 
enlargement of the original envelope of the ovum. The 
mature foetus he found to be more than one fourth as long 
as the parent, and except for the non-development of the 
9Vary, was constituted in every respect like the adult, as re- 
gards both its internal and external structure. 
For the specimens of Anableps Gronovii, upon which the 
following observations were made, I am indebted to the 
liberality of Dr. Francis W. Cragin, United States Consul at 
Paramaribo, in Surinam. Among them were three males and 
five females, four of which last were in different stages of ges- 
tation, The different individuals varied from three and a 
* Cuvier et Valenciennes Hist. Nat. des Poissons, T.i.p.540. 1828. 
t Rathké, Mem, sur Ia Develop. de l'Homme et des Animaux, 2me partie, 
Leipsic, 1833, 
¥ Cuv. and Valenciennes, Hist. Nat. des. Poiss. T. xviii. p. 245. Paris, 1846. 
$ Duvernoy, Ann. des Se. Nat. T.I. N. S. p. 313. 1844. 
Agassiz, Am. Journal of Science. Vol. XVI. Second Series, Nov. 1853. 
