CESTOIDEA. 1 7 



The presence or the absence of echinococci in an 

 hydatid do not indicate any difference in the natm-e 

 or in the species of that vesicle, for it is not an 

 uncommon occurrence to find in the same cyst 

 hydatids, which are exactly alike as regards their 

 appearance, some of which contain echinococci, whilst 

 the others do not. 



Rudolphi has distinguished three species of echi- 

 nococci, — E. hominis, E. simice, and E. veterinorum, 

 but this distinction has been founded more upon the 

 habitat of the worm than upon its zoological charac- 

 ters. Dujardm only describes the E, veterinorumy 

 and Diesmg places all the echinococci in one species, 

 E. jpolymorjphus. Ktichenmeister divides them into 

 two species, — the E. veterinorum, which he calls 

 E. scolicipariens, and the E. horainis, which he calls 

 E. altricipariens ; this distinction appears to be 

 founded more upon theoretical views than upon pre- 

 cise points of difference between the two species. 



Genus (?) Cysticercus. — This is a solitary cestoid 

 worm, provided with a voluminous caudal vesicle, 

 with a head which possesses a double circlet of hooks 

 and foiu* suckers, with a neck, and with a more 

 or less developed body, which is subcylindrical or 

 flattened and marked by transverse furrows. 



The body of the cysticercus presents deep fur- 

 rows, but not segments completely separated like 

 those of the taenia ; it incloses a large number of 

 calcareous corpuscles, but none are found usually in 

 the caudal vesicle ; the caudal vesicle is endowed 

 with well-marked contractility, which it probably 

 loses when it has grown old. In the majority of the 

 cysticerci the head and the body are retracted and 



c 



