ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 895 



wMch the maturation pouch is wanting, and where the detached egg 

 falls into the general cavity, these granules are seen to circulate and 

 spread everywhere in the body, even in the limb and pedicel, finally 

 uniting with the egg, which also grows rapidly. In these facts the 

 author sees a sketch of what happens in many Turbellarians and in 

 the Trematoda. 



Winter-egg. — The much-discussed winter-egg is regarded by 

 Huxley not as a true egg, but as a portion of the ovary separated from 

 the rest ; a sort of composite of several eggs. He does not admit that 

 these eggs undergo segmentation after laying. M. Joliet is able to 

 affirm that the winter-eggs are formed in Melicerta exactly in the 

 same way as summer-eggs, and, like them, segment after deposition. 

 What has probably deceived the eminent observer is the fact that the 

 vitelline granules of the winter-egg, being extremely opaque, darken 

 very much the stroma of the ovary which secretes them. The first 

 phases of segmentation are identical in both cases ; it is difficult to 

 follow the transformations in all their details, owing to their extreme 

 opacity, but the general progress is exactly the same. As the de- 

 velopment advances, the egg becomes lighter in hue till it takes a 

 citron tint which it retains throughout the winter. It is then covered 

 by an internal ornamented shell and formed of " parchment cells." At 

 the end of winter, as a rule, this latter shell alone remains, and 

 towards March or April there issues from it a small, but perfectly 

 formed Melicerta which does not pass through the phase of a ciliated 

 and swimming larvae, as does that from a summer-egg. 



Male Summer-egg.— This has a similar development to that of 

 the female summer-egg, at least as far as the closing of the blastopore. 

 The animal which issues from it is about haK as small as the female 

 larva, which it resembles in its general form, but it differs from it in 

 the complete absence of the digestive tube, and in the presence of an 

 organ which, by analogy with the male of Lacinuiaria, the author 

 considers to be a sperm sac, though as yet he has not discovered any 

 spermatozoid in it, but at most mother-cells. This may be because 

 he has always observed the male shortly after it has hatched out, and 

 has not made any observations on its role. It is rare, dies speedily, and 

 has never been seen in any tube of a female. Whether it fecundates 

 all the females, or only those from winter-eggs, or whether the repro- 

 duction is exclusively parthenogenetic, the author is not able to decide. 

 Nor has he been able to observe in any female anything resembling a 

 spermatozoid. 



The egg from the maturation pouch is covered with a thick 

 chorion : it always commences to segment immediately after laying, 

 and apparently under the action of the water, for the egg ready to be 

 laid which remains in a dead female, does not segment, but perishes, 

 unless the chitinous envelope of the mother is torn so as to admit 

 the water, in which case the egg soon commences to develope. 



E chine dermata . 

 Echinoidea of the ' Challenger ' Expedition. — The full report 

 of Prof. A. Agassiz has now been published, extending over 300 pp., 



