6oo 



CESTOIDEA 



like Hymenolepis murina, which is said to have its larvae in 

 the villi and its adults in the intestine of the rat, infest only 

 one host. 



Often the Cysticercus is found in a herbivorous animal, while the 

 tapeworm occurs in a carnivorous or omnivorous animal. Infection 

 is direct by feeding, for in the alimentary canal the cyst dies off, and 

 leaves the scolex, which develops in the course of a few weeks into 

 an adult tapeworm, whose span of life appears to be about a year, 

 but may be much more or much less. An example is Cysticercus 

 fasciolaris of the mouse, which becomes Tcenia crassicollis in the cat. 

 Abnormahties are often met with in the segments. 



Habitat. — ^As a rule the adult lives in the alimentary canal usually 

 of a vertebrate, but they may be found in the liver and pancreas. 

 They are capable of active movements during life. Food is obtained 

 by osmosis from the contents of the alimentary canal. 



Classification. — The classification fohowed is that of Monti- 

 celli, given by Braun in Bronn's ' Klassen und Ordnung des 

 Thierreichs.' 



The Cestoidea Rudolphi, 1808, are divided into Cestoidaria Monti- 

 celli, 1892, which are Cestodes consisting of a single segment con- 

 taining a single set of reproductive organs, and Cestoda sensu stricto 

 Monticelli, 1892, which are the typical cestodes with a scolex and 

 segments. The subclass Cestoda are divided into orders as follows : — 



Cestoda Sensu Stricto Monticelli, 1892. 



Synonyms. — Pollaplasiogonei E. Blanchard, Cestodes digeneses van 

 Beneden, C. polyzoa Lang. 



Definition. — Cestodes in which the adult worm consists of a 

 scolex and proglottides. 



Order I. Pseudophyllidea Cams, 1863. — Synonyms.— 5o/Ano- 

 cephaloidea. — -Scolex armed or unarmed, with two usually slightly 

 developed, groove-like suckers, with three genital orifices. Vitel- 

 laria situated laterally. Eggs with or without a lid. 



Order II. Tetraphyllidea Carus. — Scolex armed or unarmed, 

 with four very motile pedunculated or sessile bothridia, or with 

 four round suckers; no uterine orifice; cirrus and vagina open at 

 the sides. Vitellaria situated laterally. 



Order III. Cyclophyllidea van Bened'en.' — Scolex with four 

 suckers, between which there is an apical rostellum with or without 

 hooks; segmentation distinct; no uterine orifice; vitellogene gland 

 single, placed behind the ovary. Eggs without lids. 



Order IV. Diphyllidea Cams.- — Head stalk armed with hook- 

 lets, with solex, rostellum, and two bothridia. 



Order V. Trypanorhyncea Diesing. — Scolex with two or four 

 bothridia, and four retractile armed rostella. 



The only orders which contain parasites found in man are I. 

 and III. 



