320 THE VOYAGE OF H.M.S. CHALLENGER. 



1859. Valette, St. George, A. J. H. de la. 



I860. 



Ueber die Entwicklungs-geschiclite der Amphipoden. Sitzungsber. Nieder- 



rhein. Gesell. f. Natur- u. Heilkunde zu Bonn, XVI. pp. 94-98, 1859. 



Studien iiber die Entwickelung der Amphipoden, Mit 2 Tafeln. Halle. 1860. 



14 pages. 2 Plates. 



The ovaries are described as lying dorsally upon the gut and liver-tulDes on either side of the 

 heart, forming two cylindrical tubes closed at either end, reaching from the second to the 

 sixth peraeon-segment with an oviduct opening in the fourth segment. The inner surface is 

 covered by an epithelium layer which is supported by a Tunica ^wopria of finely granular 

 appearance, and that in turn is surrounded by an outer skin which is homogeneous. 

 [Bruzelius traces the ovaries from the first to the seventh segment, with the opening of the 

 oviduct at the base of the marsupial plate of the fifth segment. G. 0. Sars traces the 

 ovaries from the second to the seventh, with the opening of the oviduct as stated by 

 Bruzelius in the fifth segment]. Neither la Valette nor Bruzelius could discover the lobes 

 of which according to Spence Bate (1855) the ovary of Gammarus is composed. 

 The fiist origin of the Amphipod-egg is derived by la Valette from an epithelial cell of the ovary. 

 In eggs not far developed he found a sharply defined membrane, a finely granular content, 

 a germinal vesicle and many germinal spots. With further development of the egg-cell 

 violet-coloured drops appear in the hitherto colourless contents, which soon as smaller or 

 larger strongly refracting globules fill the whole egg and conceal the germinal vesicle. The 

 coloured yolk develops itself within the cell-membrane. 

 La Valette could never succeed in observing zoosperms in immediate proximity to the egg or 

 within it. Of the two skins of the egg one in later stages of the embryo's development 

 sometimes disappears, but the one remaining is not, he says, as Meissner supposes, the 

 chorion or outer, but always the inner, or yolk-skin. The inner skin has a finely shagreened 

 appearance ; the outer is completely homogeneous. 

 He thus sums up his view of the earlier stages of the development of the egg. An epithelial cell 

 of the ovary increases in size, its nucleus becomes the germinal vesicle and fills itself with 

 germinal spots, while within the ceU-membrane the development of the fine-grained yolk 

 begins. Along with this and perhaps partly at its expense along with the increasing size of 

 the egg appears the violet yolk. The former he calls the formation-yolk, the latter the 

 nourishment-yolk, which at successive stages changes from violet to brown-red and finally 

 to yellow-brown. The formation-yoLk divides and perhaps with it the germinal vesicle. 

 In this way arise the yolk-balls including a nucleus, and these after continued division by 

 hardening at the periphery obtain a membrane and become the cells of the embryo-skin. 

 When this has completely sheathed the nourishment-yolk, the whole egg-content draws 

 back on one side from the egg-skin, and by a constriction on that side is divided into two 

 unequal portions still connected on the opposite convex side. On the side where the con- 

 striction has taken place the cells of the embryo-skin put out isrotuberances, marking the 

 position of arteries, mouth-organs and limbs. 

 A full discussion follows of the micropylic apparatus of the Amphipod-egg, which Meissner fii-st 

 discovered in Gammarus pulez. It is confined to the inner or yolk-skin, the outer skin or 

 chorion being completely closed. It lies, not as Meissner supposed, at the pole of the egg, 

 but near the greatest diameter of its breadth. At its central point is a small tap with two 

 small openings. The apparatus occurs at the part of the egg corresponding with the back 

 of the embryo and the third perseon-segment of the developed animal. It is attached to a 

 spherical sack which extends into the heart of the embryo, and which is still observable in 



