VERMES, CCELENTERA AND PROTOZOA. 171 



from the generative pore. In Caryophyllaeus, although 

 there is, as in the Bothriocephalidae, a separate vagina 

 and uterine duct, these join together and open at the 

 generative pore as a single duct. 



But perhaps the most important part of Will's work 

 lies in his account of the nervous system. He finds in 

 the trunk ten nerve cords running longitudinally down the 

 body. Of these, two run laterally within the longitudinal 

 layer of muscles, and are considerably larger than the others. 

 These he calls the principal trunks (" hauptstamme "). Of 

 the remaining eight, all of which run outside the circular 

 muscular layer, two are situated dorsally, two ventrally, and 

 four laterally. The four lateral nerves of the outer layer 

 are situated close to the principal trunks, although separated 

 from them in the body region by a thin layer of muscles, 

 but in the region of the neck they fuse with them ; so that 

 there only six trunks in all can be seen in transverse 

 section. In the head, the six lateral nerves break up into 

 a complicated anastomosis, in which may be recognised two 

 principal ring commissures, and twelve main cephalic nerves. 



In other Cestodes, such as various species of Taenia, 

 Acanthobothrium coronatum, etc., ten longitudinal nerve 

 cords have been described, two principal trunks and eight 

 smaller accessory ones. In the group of the Trematoda, 

 on the other hand, only six lateral nerves have been 

 recognised, of which the two ventral are the thickest and 

 most important. Will considers, after a careful examina- 

 tion of the histology of the nervous system, that the four 

 lateral accessory nerves of Caryophyllaeus ought to be 

 considered part of the principal lateral trunks, and, con- 

 sequently, that the nervous system of Caryophyllaeus 

 shows greater affinities with that of the Trematodes than 

 with that of the Cestodes. Caryophyllaeus then must 

 remain among the Cestoda, but in the simple unsegmented 

 form of its body, in the arrangement of the sexual organs, 

 and in the character of nervous system it is more primitive 

 than the other tapeworms. 



Considerable interest has been aroused recently by a 

 controversy which has been going on for some time past 



