6 ENTOZOA FOUND IN MAN. 



Chapter II. 

 CESTOIDEA. 



The entozoa which belong to this class are composed 

 of a soft, and usually flattened body ; they have no 

 mouth nor intestinal cavity ; calcareous corpuscles, 

 ordinarily very numerous, are scattered about in 

 various parts of the body of the worm ; there is 

 usually a head (known as the nurse, or scolex), fur- 

 nished with two or four little depressions (known as 

 suckers), which are muscular and very contractile, 

 and are often armed with hooks, arranged either in 

 a terminal circlet around a small tube (called the 

 rostrwm or rostellum), or in pairs in front of each 

 sucker, or else in considerable number upon four 

 retractile tubes ; the body of the worm (called 

 strobile) is formed of numerous pieces, or rings ; 

 these either remain for a long period continuous with 

 each other and with the head, or are soon detached, 

 and live for some time in a free state, when they are 

 spoken of as cucurhitini or proglottides ; four rami- 

 fying longitudinal canals may be observed upon the 

 head and the rings ; — these possibly serve the purpose 

 of an excretory apparatus. The embryo is usually 

 oval-shaped, and armed with six hooks, from which 

 circumstance it derives the name of hexacanthus. 

 The larva undergoes various transformations, but is 

 sometimes multipUed in the same form by gemmation. 

 The cestoidea are the most common of all the 

 entozoa. They comprise a very large number of 

 species which, in their difierent stages, occupy all of 

 the viscera of vertebrated animals. The cestoid 



