TAPEWORMS. 43 



The proglottides or segments as they hecome ripe pass out of 

 the host and lead a free Hfe for a short time : they are the 

 reproductive parts, whilst the scolex and neck are the vegeta- 

 tive parts, of the cestode. Tet each segment is practically an 

 individual animal. The internal structure, like the external, is 

 simple ; no alimentary canal will he seen at all ; each segment, 

 which may be ohlong or square, broad or narrow, according to 

 the species, is nearly solid throughout. Beneath the outer 

 layer or cuticle is a matrix of small cells, in which glandular 

 cells are seen to be dotted about ; beneath this is a thin layer 

 of longitudinal muscle, then a parenchymatous mass of connec- 

 tive tissue in which small bundles of longitudinal muscle-fibres 

 are scattered, then a layer of circular muscles, and finally in 

 the centre of the segment the organs are embedded in a solid 

 connective tissue. In the first segments we find dotted about 

 calcareous bodies, that are calcified connective tissue-cells. Each 

 segment has its own generative apparatus, both male and 

 female organs being found in each proglottis. The male 

 organs consist of a number of pear-shaped bodies, the testes 

 (fig. 10, T) ; each of these small round male glands has a fine 

 duct running from it. These vasa efferentia, as they are called, 

 unite into a common duct, the vas deferens {Vd), which is 

 spirally coiled at the end ; this portion lying in a muscular 

 pouch, the " cirrus pouch," it can be protruded as the penis 

 or cirrus (P). The female organs are more complicated : they 

 consist of two ovaries {Ov), yolk-gland, uterus {Ut), shell-gland, 

 receptaculum, and vagina {Vg), situated as shown in fig. 10. 

 The vagina generally opens into the same cavity as the cirrus, 

 but may be separated from it some distance. 



The Tapeworms are also provided with an excretory system 

 (fig. 10, Wv), which extends as four tubes united transversely in 

 each segment, and finally all uniting and opening by one vesicle 

 at the last segment. The nervous system is very primitive, 

 consisting of two cephalic ganglia in the scolex united by a 

 commissure, and two long lateral trunks (iVe) running down 



