GENERATIVE ORGANS OF NEMATOIDA. 295 



is usually tolerably long and without epithelium ; it corresponds 

 with Nelson's oviduct. At the point of transition from two into 

 three, the lateral daughter-eggs separate from their germ-cells. 

 In the Nematoidea, at least in the Ascaricles, it presents the 

 peculiarity that very large nucleated cells, with granular tenacious 

 contents, are placed upon the inner surface of its proper tunic ; 

 each of these forms a tubercular, very decidedly villous, tongue- 

 shaped ridge, projecting far into the interior of the tube. These 

 villi, bursting, scatter their contents, Avhich are then employed 

 for the formation of the egg-envelopes, as we shall see further on, 

 amongst the processes which go on after fecundation. In the 

 nearly allied Mermis, this tube consists of alternating Haustris 

 (like the large intestine of a rabbit), and of small chambers, 

 along the whole length of the tube, which are caused by circular 

 folds projecting into its interior. The latter constantly become 

 more and more rare towards the Tuba, cease at length, and 

 become changed for a net of polygonal cells. Instead of the 

 epithelium, we observe here in the walls, scattered, very large, 

 clear, delicate, longish cells, with one or two small dark nuclei, 

 never reaching beyond a neighbouring chamber ; besides pale, 

 large, tenacious, and adherent globules, (probably, albumen- 

 globules). The eggs found in this tube are still for the most 

 part triangular, but round in some species [Mermis), and at first 

 furnished with an opening in the vitelline membrane, (that is, 

 the still uncicatrized remains of the stem), to which Keber has 

 given the very suitable name of the micropyle. However, the 

 mutual cohesion of the whole contents of the albuminigene in 

 the Ascaricles, is a serious hindrance to the tracing of the process 

 here described, for which the Mermis albicans is especially 

 adapted. 



4. The Tuba. — It is short, narrow, the thinnest part of 

 all, but may be greatly thickened by the deposition of mus- 

 cular fibres (longitudinal and annular fibrous layer), destitute 

 of epithelium, and in Mermis furnished with folds, which pro- 

 bably contribute to its dilatation. As in the albuminigene, each 

 egg enters here separately. In consequence of the pressure of 

 its wall against the long sides of the eggs, and the pressure upon 

 their poles, we usually find in it a more quadratic form of egg, 

 which often acquires the round form quite suddenly under the 

 eye of the observer on entering into the fundus uteri. In the 

 portion of this division nearest to the albuminigene, as also some- 



