CESTOIDEA 



597 



The head is provided with muscular suckers, which keep it attached to the 

 mucous membrane of the bowel. Often there are also hooks presept on some 

 part of the head, not infrequently on an anterior pro- 

 jection called the rostrum. The neck is constricted, 

 and shows posteriorly faint rings indicating the com- 

 mencement of new segments, which are always formed 

 from the neck. 



Behind the head come the proglottides, the youngest 

 being those situated anteriorly, and the most fully 

 developed posteriorly. Their number is very variable, 

 and their size increases from before backwards. They 

 contain the male and female sexual organs. 



The whole surface of the worm is covered by a thick, 

 non-chitinous cuticle,said to contain a quantity of lime 

 salts, under which lies a basal membrane ; beneath this 

 come the cuticular muscles, and then the cortical 

 parenchyma, in which lie the sunken epithelial cells, 

 nerve cells, sense organs, excretory cells, etc. Among 

 these cells are peculiar calcareous corpuscles, varying 

 from 3 to 30 ^ in diameter, and having essentially the 

 structure of a fat cell — -that is to say, they are composed 



of concentrically deposited calcareous material enclosed in a cell with a nucleus 

 at one side. These corpuscles are highly characteristic of a Cestode. The 

 calcareous matter is composed of 79 per cent, organic matter and 21 per cent, 

 of lime salts, in the form principally of the carbonate, but also of an albuminate 

 and a urate. Their function is not understood; perhaps it is skeletal, perhaps 

 protective. 



. 238, — Head of 

 Tcsnia solium. 



(After Leuckart.) 



> ^'■■'iooooco 

 ,000 00 uoS, 



Fig. 239, — Mature Segment of TcBnia saginata Goeze, 1782. 

 (After Leuckart.) 



In the cortex come the longitudinal muscles, beneath which are the trans- 

 verse muscles, which enclose a central area of the parenchyma called ths 

 medullary layer, and therefore separate cortical from medullary layers. 



There is no alimentary canal, and the excretory system with its flame cell 

 terminations consists of anastomosing capillaries emptying into a dorsal and 

 ventral collecting tube on each side of the body, wliich run from the scolex to 



