PLATYHELMIA. 43 



minute rounded spermaries (f), from which proceed exceedingly 

 delicate ducts that by their continued union form a spermiduct (v.d). 

 This is continuous with a muscular, eversible penis (p) (cirrus), 

 contained in a cirrus-sac (c.s) and opening into a depression, the 

 genital atrium (g.a) which occupies the summit of the genital 

 papilla. 



Each spermary essentially consists of germinal cells (sperm- 

 mother-cells) each of which produces a number of sperms. In 

 this process the nucleus divides repeatedly to form the heads of 

 the sperms, and their vibratile tails are then differentiated from 

 the protoplasm. (2) The female organs consist of two ovaries, 

 an oviduct, uterus, vagina with spermotheca, a yolk-gland, and a 

 shell-gland. 



The ovaries (ov) are collections of much branched tubules situ- 

 ated in the posterior part of the proglottis. These tubules unite 

 to form an oviduct which communicates on the one hand with a 

 blindly ending tube, the uterus (ut), and on the other with a 

 vagina (v), dilated internally into a spermotheca (sp) and opening 

 into the genital atrium. The yolk-gland (yk) is a tubular network 

 situated behind the ovaries and opening into the oviduct, which 

 also receives in this region the numerous minute ducts of the 

 unicellular elements which make up the rounded shell-gland 

 (sh.g). 



Self-fertilization appears to be the rule, and takes place, after 

 closure of the genital atrium, by contractions of the spermiduct 

 and penis the result being that sperms are forced through the 

 vagina to the spermotheca, and thence' to the oviduct, where they 

 meet with and fertilize the ova. Each fertilized ovum, together 

 with a number of yolk-cells, is surrounded by an egg-shell to 

 constitute an egg, and the eggs pass on to the uterus. 



The tapeworm possesses considerable power of movement, being 

 able to elongate or shorten itself, raise or lower its hooks, and 

 attach or detach its suckers. The muscles by which these various 

 movements are made consist of (1) a superficial longitudinal 

 layer by which the body can be shortened, (2) transverse muscle- 

 bands situated more deeply and serving to elongate the body, 



(3) dorso-ventral fibres by which the proglottides can be flattened, 



(4) radial and circular muscles in the suckers, and (5) minute 

 elevator and depressor bands attached to the hooks. 



The muscles are for the most part attached to the firm cuticle, 



