172 



ZOOLOGY FOR MEDICAL STUDENTS 



CHAP. 



main longitudinal excretory tube which runs along each side of the body^ 

 passing uninterruptedly through the chain of proglottides. The two 

 tubes are connected in ladder-like fashion close to the hinder limit of 

 each proglottis and in the last proglottis of the chain the transverse 

 corinectihg channel opens to the exterior. 



The nervous system consists of numerous sensory cells connected 

 with a network or plexus of nerve fibres lying just below the epidermis, 

 this network being connected in turn with a series of longitudinal trunks 



Fio. 78. 



Taenia serrata. A, Complete tape-worm ; B, scolex m side view ; C, scoiex, end view. A, Hooks ; 

 t, rostellum ; S, scolex ; s, sucker. 



lying at a deeper level. Of these longitudinal trunks there are ten, two 

 of which, situated laterally, just external to the main excretory duct, 

 are larger than the others. The longitudinal trunks are connected by 

 numerous irregular commissures of which there is a specially complicated 

 arrangement in the " head " region. 



The reproductive organs are hermaphrodite and of much complexity. 

 The male gonad consists of numerous small spherical testes (Fig. 79, A, t) 

 scattered throughout the parenchyma, each having a slender tubular 

 vas efierens connected with it. The vasa efierentia become joined to- 



