256 



COMPARATIVE ANATOMY 



CHAP. 



and this emerges by a short and narrow terminal piece, the duetus 

 ejaeulatorius, into the cloaca. Above the duetus ejaculatorius there 

 often lie two elongated sacs, invaginations of the cloaca. Each sac 

 contains a chitinous spiculum. In copulation the spicula may be 

 protruded from the cloacal aperture by special muscles attached to the 

 spicular sacs. In the female genital apparatus (Fig. 169) each of 

 the paired genital tubes repeats in essentials the divisions of the male 

 apparatus. The extraordinarily long ovarial tube lies in numerous 

 windings in the body cavity. In its axis there also lies a rachis, to 

 which the young eggs are attached. The ovarial tube is continued 

 into a wider part, the uterus, at whose commencement fertilisation 

 generally takes place, that is if the eggs have not already been fertilised 

 in that terminal portion of the ovarian tube into which the rachis does 

 not reach. The uterus contains fertilised eggs in the first stages of 

 their segmentation, and even young embryos. The two uteri unite at 

 their ends and pass into a short common terminal division, the vagina, 

 which is often muscular, and opens outwardly in the ventral middle 

 line through the female genital aperture. 



2. Gordiidse. The genital apparatus of the Gordiidce is quite 

 different from that of the Nematoda. The male apparatus also is 

 paired. The male and female genital apertures emerge into the last 

 division of the intestine (cloaca). The female genital glands (Fig. 

 170) are lobed ovaries which lie in large numbers in pairs one behind 



the other on both sides of the 

 dorsal mesentery. They are 

 developed very late at the 

 expense of the mesodermal 

 cells, which in the young 

 Gordiidse almost entirely fill 

 the body cavity. Some of 

 the eggs which ripen in the 

 ovaries reach the body cavity, 

 entirely filling its lateral 

 chambers and so forming 

 those masses of eggs which 

 were formerly erroneously 

 considered to be ovaries. The 

 further fate of these eggs is 

 not known. Another portion 

 of the eggs, however, pass 

 out of the ovaries into two 

 tubes lined with epithelium which lie in the dorsal mesentery. These 

 tubes, which might be called uteri, run backwards, and when approach- 

 ing the posterior end of the body become narrow and bend round as 

 oviducts to the ventral side, where they enter a pear-shaped glandular 

 accessory organ of the small degenerating cloaca, the atrium. There 

 is further an unpaired vesicle, the receptaeulum se iis, placed under 



^__ iOT _^^^ md 



BD 



Fio. 170. Transverse section through Gordius, 

 after Vejdovsky. Ih, Body cavity ; c, cuticle ; hy, hypo- 

 dermis ; u, uterus ; Im, longitudinal musculature ; et, 

 endothelium of the body cavity ; ov, ovarium ; mes, 

 mesenteries ; md, mid-gut ; bm, ventral chord. 



