244 



ZOOLOGY 



SECT 



but that side towards which the female reproductive organs are 

 more nearly approximated is regarded as the ventral, the opposite 

 as the dorsal surface. On one border, alternately on the right 

 and left of each proglottis, is a little prominence, the genital 

 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 



ut. 



FIG. 196. Transverse section of Tsenia soliuxn. c.m. circular layer of muscle ; ex. longitu- 

 dinal excretory vessel ; ne. longitudinal nerve : o.d. oviduct ; ov. ovary ; te. testes ; 

 trf. uterus. (After Shipley.) 



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. 197, 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 

 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 



