658 BNTOZOA. 



SECOND STTB.ORDER. ACANTHOCEPHALA, (Gr. from ayavda, 

 akantha, a thorn ; xeqpaXj?, kephale, a head.) HOOKED WORMS. 



This order contains but one genus, Echinorhynclms, (Gr. echi- 

 nos< a hedge-hog ; rhunchos, beak,) with numerous species. The 

 generic name refers to the chief character, which is a straight, 

 round trunk, armed with rows of recurved tooth-like hooks. 

 These Worms are generally found in the intestinal canal ; some- 

 times in the neck under the skin. They occur in all vertebrates 

 except man, sometimes boring through the intestines and passing 

 into other parts of the body. The species E. gigas, which is 

 from three to fifteen inches long, infests hogs, particularly such 

 as have been shut up to be fattened. 



THIRD SUB-ORDER. TREMATODA, (Gr. from T^wa, trema, a for- 

 amen or hole.) FLUKE WORMS. 



These worms have a soft and rounded or flattened body. The 

 head is indistinct, with a suctorial foramen ; one or more sucto- 

 rial pores appear on the surface of the body, furnishing the ba- 

 sis of their subdivision into genera. They have no intestinal 

 canal. The Fasciola, (Lat. a small bandage,) hepaticum, (Gr. 

 hepaticos, of the liver,) is a representative of this group, a 

 worm that infests the liver, gall-bladder, and sometimes the con- 

 tiguous veins or ducts ; is frequently found in numerous rumi- 

 nant and other animals. It is particularly common in sheep, in 

 the disease called the rot. This worm has sometimes been found 

 in the gall-bladder of man. Its shape is considerably like that 

 of a melon seed, (Plate XVI. fig. 8.) These worms have two 

 pores, one in front, the other ventral ; hence they are sometimes 

 denoted by the generic term, Distoma, (Gr. two-mouthed.) 



Some Trematods occur in birds and fishes. 



FOURTH SUB-ORDER. CESTOIDEA, (Gr. from xecrros, kestos, a 

 band ; eidos, eidos, form.) TAPE WORMS. 



Of these worms eight genera have been described. The 

 head varies greatly in the different genera ; generally it has two 

 or four pits or suctorial orifices, and sometimes four retractile 

 tentacles. There is no trace of an intestinal canal, unless it be 

 connected with vessels proceeding from the suckers. Two gen- 

 era contain species that infest the human body : 



1. Bothriocephalus, (Gr. lothros, a groove ; kephale, head.) 

 This is a long, flat, jointed worm, with two longitudinal grooves, 



