VI 



PHYLUM NEMATHELMINTHES 



309 



ciliary flames ; at the end of each lobe are a number of fine perforations 

 placing the contained canal in communication with the body-cavity. The 



stalk of each nephridium con- 

 tains a single main canal ; these 

 unite to form a wide median 

 dorsal channel which opens 

 behind in the female into the 

 unpaired portion of the oviduct 

 and in the male into the ejacu- 

 latory duct. 



The greater part of the body- 

 cavity is occupied by the repro- 

 ductive organs. The sexes are 

 separate, and the female is 

 larger than the male. In both 

 sexes the gonads and their ducts 

 are connected with a great sus- 

 pensory ligament (s.lg.), which 

 extends backwards from the end 

 of the proboscis-sheath. 



In the male there are two 

 ovoidal testes (Fig. 255, is.) con- 



FIG. -57. A, longitudinal section through the 

 terminal twigs of the nephridia of Echino- 

 rhynchus gigas ; highly magnified, a, 

 nucleus. , a terminal twig more highly mag- 

 nified. 6, the porous membrane. (From Shipley, 

 after Kaiser.) 



nected with the suspensory ligament. From each a 

 furnished with several vesiculce seminales or sacs for 

 the storage of spermatic fluid, passes backwards and 

 unites with its fellow to form an ejaculatory duct, with 

 which are connected about half a dozen cement glands 

 (c. gl.}. The ejaculatory duct opens into the bursa or 

 bell-like copulatory organ (6), and has at its opening a 

 small papilla acting as a penis. 



In the female the ovary is connected with the 

 suspensory ligament (Figs. 256 and 258, s.lg.}. When 

 ripe, groups of ova known as the " swimming 

 ovaries " (s. ovy.) become detached and swim freely 

 in the body-cavity, where they are impregnated. The 

 ducts are very peculiar. Connected with the end of 

 the suspensory ligament is a muscular uterine bell (6.), 

 widely open anteriorly (Fig. 258, 2.) into the ccelome, 

 and having towards its posterior end a small aperture 

 or a pair of small apertures (?/), also communicating 

 with the ccelome. The bell is connected with a narrow 

 double passage leading to a uterus (ut.), which itself 

 opens by the genital aperture at the posterior end of 

 the body. The uterine bell performs rhythmical 

 swallowing movements, and as the eggs containing 

 partly developed embryos float in the ccelome they 

 are swallowed by the bell. The immature eggs, which 

 are globular, are passed back into the ccelome through 

 the posterior aperture (y] of the bell ; but the mature 

 eggs, which are spindle-shaped and covered with a 

 chitinous investment, make their way from the bell to 

 the uterus through the narrow passages, and so to the 

 vagina. 



The early stages of development take place in the 

 ccelome. Segmentation is regular, and a peculiar form 

 of gastrula is produced, having neither archenteron nor 

 blastoccele in other words the ectoderm and endo- 

 derm are in close contact with one another, and no 



vas defer ens (v. df.), 



-ut 



FIG. 258. Female organs 

 of Echinorhynchus. 

 b. uterine bell ; s. Ig. 

 suspensory ligamen t : 

 ut. uterus ; vg. vagina ; 

 x. y. apertures of bell ; 

 z. apertures leading 

 from bell to uterus, 

 (After Hertwig.) 



