30 ENTOZOA FOUND IN MAN. 



Chapter III. 

 TEEMATODA . 



These are solitary, non-articulated animals, more or 

 less elongated and flattened ; they are provided with 

 one or several organs of adherence, or suckers, with a 

 soft integument not covered with vibratile ciha, with 

 a mouth, and with an intestine, which is usually 

 bifinrcate, sometimes simple, sometimes ramifying, 

 and which always has a coecal termiaation ; they 

 possess a nervous system, which is formed by a 

 central mass and two lateral cords, and also a 

 system of excretory canals ; they do not possess 

 any circulatory apparatus ; they are generally her- 

 maphrodite. 



The trematode worms present two secondary 

 t3rpes, which are completely distinct both as regards 

 their organization, their mode of development, and 

 their kind of life. 



The first is that of the Polystoma (the Trema- 

 toda monogenesia of Van Beneden), and comprises 

 those trematode worms which are fiunished with 

 more than two suckers. They have a direct develop- 

 ment ; the embryo, which is unprovided with cilia 

 at the moment of its being hatched, already possesses 

 the form of the adult. All of them live as external 

 parasites, upon the integument or the gills of aquatic 

 animals, chiefly fishes ; they are never enclosed in 

 a cyst. 



It is unnecessary to give any further description 

 of this type, as it has not been observed in Man. 



