ANATOMY OF THE NEMATODES 369 



the uterus proper. (For the explanation of the terms convergent and 

 divergent uteri vide footnote p. 432.) Uterus and ovaries, which arise 

 in the first place from a single cell, lie between the body wall and the 

 gut and are surrounded by connective tissue. In some species (for 

 instance, Trichinella) the ovary is single. 



At the blind end of the ovary there is a mass of protoplasm with numerous nuclei 

 that multiply continuously. Gradually the nuclei arrange themselves in longitudinal 

 rows (fig. 265) and the protoplasm commences to leave the periphery and surround 

 each nucleus. The nearer to the uterus the more progressive is this loosening 

 process, until club-shaped cells each containing a nucleus are developed. The most 

 pointed end of each, however, is still attached to an axial fibre of protoplasm, the 

 rhachis j probably this has some connection with the nutrition of the ova. Finally 

 the ova fall off and reach the uterus, where they are fertilized and enclosed in shells. 



(6) Male Sexual Organs. There is never more than one testis 

 (fig. 266), which is a straight or sinuous tube of the same construction 

 as an ovary, and in which the mother cells originate in the same 

 manner as the ova. In the same way as the ovary passes into the 

 uterus, so does the testis pass into the spermatic duct ; the latter is 

 often divided into the somewhat dilated seminal vesicle and into 

 the muscular ductus ejaculatorius, which, running ventral to the 

 intestine backward (fig. 267), finally opens into the cloaca. In 

 many species, e.g., A. duodenale, the ejaculatory duct is surrounded for 

 a greater or less portion of its extent by the cement gland, the secretion 

 of which (brownish or blackish in colour) serves for copulation. The 

 ejaculatory duct of the large Ascaridce is for the most of its course 

 surrounded by a muscular network which takes its origin from the 

 two dilator cells of the gut (fig. 

 268 F.). The spermatozoa of the 

 Nematodes, it may be noted, only 

 attain their full development after 

 the sperm mother cells have been 

 conveyed by copulation into the 



c ,, f , -A 1- FIG. 265. Transverse section through the 



Uteri Of the female gemtalia. In ovarian tube of Belascaris cati of the cat 



their form (sheathless, capable of at va u s levels. To demonstrate the 



, -j , v Al _ j-rv f development (right to left) of the ova and 



amoeboid motion) they differ from O f the rhachis. Magnified, 

 those of most other animals. 



SPICULES. The male genital apparatus is also provided with one 

 or two sacs, situated on the dorsal side of the intestine, and opening 

 into the cloaca. In each sac there is a chitinous rod-like body, the 

 spicule. Further, in many cases there exists, more or less fixed in the 

 dorsal wall of the cloaca, a chitinous structure, the accessory piece or 

 gubernaculum, the latter name implying its function of guiding the 

 spicules during copulation (fig. 26^). A special muscular apparatus, 

 24 



