50 DEVELOPMENT OF CESTODES. 



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 gemmtive apparatus, both male and 

 female organs being found in each proglottis. The male 

 organs consist of a number of pear-shaped bodies, the 1e!ites 

 (fig. 12, 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 I'os 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. 12. 

 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. 12, 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 (iVc) running down 

 each side of the proglottides. We thus see that although each 

 segment is sexually distinct and independent, and that the 

 segments can live a free life for a time, yet they are all united 

 into one animal by the nervous and excretory systems. 



Development of Cesfndes. — The male organs reach maturity 

 before the female : as soon as they are ripe, copulation takes 

 place, and the receptacle of the female becomes filled with 

 sperm, and then the female organs mature. 



The ova when fertilised pass into the uterus, which becomes 

 very distended, and the rest of the proglottis becomes absorbed, 

 — in fact the whole segment is filled with eggs. In the uterus 

 the eggs in the last segment are said to become free embryos ; 

 but this the writer has failed to detect in the many species of 



