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a locally altered portion of the carapace ; the outer valve of the 

 ephippium being a part of the outer layer of the epidermis, and 

 the inner valve the corresponding part of the inner layer. In con- 

 sequence of this arrangement, the inner valve of the ephippium, 

 containing the ephippial eggs, is not attached hy the hinge to the 

 outer valve, as has been generally stated, but actually lies at first in 

 the receptacle formed by the new carapace. The ephippium is 

 cast with the rest of the skin, from which however it soon becomes 

 detached, and continues to form an efficient protection to the eggs 

 until they are hatched. These eggs probably require to be fer- 

 tilized, but this fact is not completely proved. With one ex- 

 ception, whenever the author observed ephippia, he could also find 

 males ; and, generally speaking, the numbers of each were in pro- 

 portion to one another. Impregnation is not, however, absolutely 

 necessary to the production of ephippia, as the author has now in 

 his possession three ephippia, formed by isolated females. It re- 

 mains to be seen whether young will be developed from these or not. 

 The early stages of the agamic egg are very similar to those of the 

 ephippial egg, and consist of the enlargement, in the front part of the 

 ovary, of one of the ovarian cells, which then becomes a germinal 

 vesicle, and the deposition round it of granules, with the addition in 

 this case of oil-globules. This process continues, the other two or 

 three cells which may have existed in the same ovarian mass gradu- 

 ally disappear, and there is thus formed an egg-like mass, consisting 

 of a germinal vesicle, minute dark granules, and large oil-glo- 

 bules. When the growth is nearly completed, the vitelline mem- 

 brane is added. This is at first very delicate, but after deposition in 

 the receptacle soon becomes hard. The ovarian eggs of Daphnia, as 

 well as those of Cypris, never contain round masses like those of 

 Aphis and Musca ; but after their entry into the receptacle, yolk 

 masses are found, homologous with those present at the corresponding 

 periods in Phryganea* . The eggs when laid are about -j-g-g-o of an 

 inch in diameter ; they gradually become 2 gg , when the vitelline 

 membrane splits and falls off, and the young animal is hatched. Far, 

 however, from resembling its parent at this time, the young Daphnia 



* The round balls described by Herold in the ovarian eggs of Bombyx, appear 

 to be of a different nature, and homologous with the Nahrungsdotter mentioned 

 by Cams in spiders' eggs and the oil-globules of Daphnia. 



