192 OVARY AND PAROVARIUM, BY W. WALDEYER. 



Leydig (68), Lubbock (70), Landois (62, 63), Bessels (14), and 

 others, is similar to that of the Vanessa urticse. 



I have already stated that the ova of the higher CRUSTACEA 

 are developed in special follicles, whilst in the lower orders 

 the ovaries are simple saccules and tubules. The ovaries and 

 ova of the ARACHNIDA, respecting which we have very full 

 details in the essays of v. Wittich (127, 128), present some 

 peculiarities. The follicles are formed by lateral protrusions of 

 the tubular ovary, and, according to the above author, possess 

 an epithelial lining in the short cervical portion that connects 

 them with the ovarian tube; at a later period the yolk 

 molecules accumulate in this part of the follicle. In the first 

 instance no germ spot can be seen in the germ vesicle ; but, as 

 is shown in the illustrations given by v. Wittich, a thin investing 

 layer of protoplasm is constantly present. At first the vesicles 

 lie in close contact with the walls of the ovarian tube, which, 

 by their own enlargement and the increase of the layer of proto- 

 plasm surrounding them, they cause to protrude laterally, and 

 thus lead to the formation of the follicles. We may here also, 

 in all probability, regard the primordial eggs as simply en- 

 larged epithelial cells of the ovarian tube. (Compare A in 

 fig. 192 with v. Wittich.) A remarkable spherical concen- 

 trically laminated body, the so-called vitelline nucleus, has 

 been discovered by v. Wittich to be, in addition to the germ 

 vesicle, constantly present in the ova of some species of Araneidse, 

 it is probably identical with the similarly named body found 

 in the ova of Batrachia and Osseous Fishes. In the Batrachia 

 the yolk nucleus disappears in mature ova (Allen Thomson), 

 and in the Araneidse the central part of this body becomes 

 fluid, whilst the peripheric remains as a capsule of firm 

 consistence. The significance of the yolk nucleus is at present 

 unknown. 



DEVELOPMENT OF THE OVARIES AND OF THE OVA 

 The first traces of the sperm or germ organ, according to the 

 sex, in the embryo of the Fowl appears about the end of the 

 fourth day. At this time the Wolffian body is invested with 

 a regular columnar epithelium, whilst the rest of the peritoneal 

 cavity is lined by small flattened cells. 



