288 CONTRIBUTIONS TO THE NATURAL HISTORY 



My observations upon the developement of Hippocrene have therefore been limited 

 entirely to the investigation of the eggs, as they appear during the time they remain con- 

 nected with the maternal body. The eggs are developed in the outer layer of the walls 

 of the main digestive cavity, under the layer of epithelium which covers that organ. 

 They are imbedded between the transparent cells of the outer parenchyma, and appear 

 at first as minute transparent vesicles, which grow rapidly, and increase the bulk of the 

 central mass to such a degree as to change vastly its form (Plate II. Fig. 20, c, c, c, c, as, 

 seen from above). As soon as the eggs are ripe and ready to be laid, they assume (vvhea 

 seen from below) the appearance of four bunches of grapes united at their wider base, with 

 the smaller end turned outwards (Plate II. Fig. 23, /,/,/). Fig. 4 of Plate I. represents 

 a specimen with mature eggs, seen from above ; while Fig. 1, 2, and 3, represent speci- 

 mens deprived of eggs. After the eggs have been laid, the surface to which they adhered 

 has a furrowed appearance (Plate II. Fig. 18); it seems folded, and isolated eggs may be 

 seen still adhering in little depressions. These folds and depressions may be considered as 

 a kind of corpora lutea left in a tissue containing no vessels, and assuming, therefore, a 

 very peculiar appearance. 



The eggs themselves, when mature, show distinctly a large germinative vesicle, more 

 or less central, surrounded by a considerable quantity of yolk, consisting of granular cel- 

 lular tissue of a yellowish-white color, inclosed in the vitelline membrane. Within the 

 large germinative vesicle there is a single transparent germinative spot. Between the 

 earliest formation of the egg and this state of development, in which the yolk has not yet 

 undergone further changes preparatory to the formation of the germ, there are in the same 

 ovary eggs of very different degrees of maturity, from the most minute transparent cells, 

 already mentioned, up to larger and larger vesicles, with a more or less transparent yolk, 

 and a distinct germinative vesicle and germinative spot. But the eggs do not seem to be 

 all laid in the same state of development, for I have observed some still adhering to the 

 central cavity, in which the yolk had assumed on its surface a mammillated appearance, 

 forming a kind of mulberry-like body, probably the earliest stage of development of the 

 germ; while others were laid before they had undergone any such changes. The fact of 

 this inequality of development in the growth of the eggs in Hippocrene seems to be in ac- 

 cordance with the facts observed by Professor Forbes in the genus Lizzia, which is closely 

 allied to Hippocrene, where real buds grow from the ovary, and are developed to a con- 

 siderable degree before separating from the maternal body. In Hippocrene, however, I 

 have never seen real buds arise in that way, but have uniformly seen the eggs cast before 

 they had lost their spherical form. 



