189] PROTEOCEPHALIDAE—LA RUE 189 



the breadth of the flattened apex of the cone 0.255 mm. The suckers 

 which are separated from each other by a small zone only are very large 

 in proportion to the size of the head. The shape is oval or at times 

 triangular. Their length is about 0.306 mm. and their breadth about 

 0.136 mm. 



The head reaches its greatest breadth, 0.476 mm., at the point where 

 it passes over into the neck of medium length and a breadth of 0.348 mm. 

 First proglottids are very narrow transverse bands. The tenth pro- 

 glottid is about 0.476 mm. broad by 0.102 mm. long. As in most species 

 the length of the proglottid increases with age more rapidly than the 

 breadth. The twentieth proglottid has a length of 0.153 mm. Proglot- 

 tids near the middle of the worm are broader than long or quadrate. 

 The last proglottid is 0.765 mm. broad by 1.02 mm. long. Margins of 

 the proglottids are straight and the posterior comers of the proglottids 

 are rounded. Except for the slight elevation in the region of the genital 

 opening, the geometrical form of the proglottid is not disturbed. The 

 last proglottid is rounded off at the posterior end. 



Riggenbach (1896:196-199) described the cuticula, parenchyma, 

 musculature, and nervous system. These structures are typical for 

 Proteocephalids. He did not describe the musculature of the head. In 

 the head the small space between the suckers is almost completely filled 

 with vessels of the excretory system. The four main vessels are bent 

 inward as they enter the head. A circular anastomosis behind the suck- 

 ers could not be demonstrated. In the short apical region of the head 

 the vessels are never capillaries and an apical capillary plexus such as 

 is found in Corallobothrium lohosum does not occur. Riggenbach was 

 not able to find a direct connection of the vessels of the head or of the 

 plexus with the exterior. Posterior to the suckers the main excretory 

 vessels pass to the lateral fields of the neck in a course that is perpen- 

 dicular to the longitudinal axis of the body, then they bend posteriad, 

 decrease in size and extend throughout the strobila as nearly straight 

 narrow tubes. In the region of the cirrus-pouch and vagina the dorsal 

 vessel passes above and the ventral vessel below these organs. The ex- 

 cretory vessels lie mesad of the vitellaria and the lateral nerve trunks. 

 At the posterior part of each segment the main excretory vessels are 

 connected by a transverse anastomosis. In the region of the transverse 

 anastomosis are canals which connect the main vessels with the exterior. 

 These canals arise directly from the main vessels and not from a capil- 

 lary network. The point of opening to the exterior is on the surface 

 near the posterior angle of the proglottid. In the posterior part of the 

 end-proglottid the four main vessels join together to form a small blad- 



