248 



ZOOLOGY 



SECT. 



papilla, on which is the opening of a chamber, the genital cloaca, 

 into which both the male and female reproductive ducts open. 



An examination of entire living and of preserved and stained 

 Tape- Worms under the microscope shows (1) that an alimentary 

 system is not present ; (2) that nervous and excretory systems are 

 represented ; (3) that there is a complete set of reproductive 

 organs, constructed on the same general plan as those of the 

 Liver-Fluke, present in each of the proglottides. 



The nervous system consists of two not very well-defined 

 ganglia united by a broad transverse commissure in the head ; 

 of slender nerves passing from these to the suckers, and of two 

 longitudinal nerves which run backwards through all the proglot- 

 tides to the posterior end of the body. The ganglia seem to 

 correspond to the ganglia on the nerve-ring of the Liver-Fluke. 



The excretory organs consist of a richly branched system 

 of excretory vessels. There are four main longitudinal trunks 

 (Fig. 194, can. excret.\ two near each lateral margin in the more 

 anterior part of the strobila ; in the more posterior region one of 

 these becomes lost on each side. The two pairs of longitudinal 

 vessels are connected together in the head by a ring-like vessel 



can-.excret 



can. ejccret 



ne.ru. I 



FIG. 194. A proglottis of Tacnia SOlium with mature reproductive apparatus, can. excret. 

 longitudinal excretory canals with transverse connecting vessels ; gl. tit. vitelline glands ; 

 nerv. 1. longitudinal nerves ; ov, ov. ovaries (germaria) ; por. gen. genital pore ; schld. shell- 

 glands ; vt?.r. uterus; rar/. vagina; vas. <lef. vas deferens. The numerous small round 

 bodies are the lobes of the testes. (After Leuckart.) 



and in each proglottis near its posterior margin by a straight, 

 transverse, connecting branch. Posteriorly the longitudinal trunks 

 open into a pulsatile caudal vesicle, communicating with the 

 exterior in the last proglottis. When the latter becomes thrown 

 off, the vesicle is lost with it, and, subsequently, the longitudinal 

 vessels have their separate openings on the exterior. These 

 main trunks of the excretory system give origin to a number of 

 branches, and these in turn give off numerous fine canalicules, or 

 capillaries, terminating in flame-cells similar to those of the 

 Fluke. 



