PARASITES OP ANIMALS. 109 



bryos of the commoD. fluke. They are about ^^^ to ^^^ of an 

 inch long, and 73^2 of an inch broad. The head end is pro- 

 vided with a dagger-like boring spine, which can be alternate- 

 ly thrust out and withdrawn. It is supposed that these em- 

 bryos become parasitic in fresh-water snails, for a time, and 

 undergo transformations like those described under the pre- 

 ceding species. Their effects and remedies are the same as 

 for the common fluke, though owing to their small size they 

 would be less injurious, unless in much greater numbers. 



The Stomach-flukes of Cattle (^Amphisto7na conicum Rud. and 

 A. crumeniferum Creplin). 



The flukes belonging to the genus Amphistoma, which in- 

 cludes, besides the two indicated, A. explanatum from the 

 bile-ducts of cattle and A. truncatum from the cat, have a 

 small, rather thick, and somewhat conical body, the mouth- 

 sucker being at the small end. The large end is rounded and 

 bears the other sucker, which is always much larger, near the 

 posterior end. The stomach and reproductive organs are 

 nearly like those of Distoma. The eggs also produce ciliated 

 embryos in the water, and they are supposed to go through 

 similar transformations. I do not know that either of them 

 have been observed in sufficient numbers to produce serious 

 diseases in cattle. 



ACANTHOCEPHALA. 



(^Thorn-headed worms.') 

 Echinorhynchus gigas Goeze. Figures 74, 75. 

 This, which is the only representative of the order hitherto 

 found in our domestic mammals, is quite frequent in the intes- 

 tine of hogs. It may at once be known by the peculiar pro- 

 boscis, which bears several circles of small but sharp hooks, 

 which are arranged alternately, in quincunx, mostly toward 

 the end of the proboscis (Figure 75) . These worms have a 

 long roundish body, tapering to the posterior end. The skin 

 is generally crossed by numerous transverse wrinkles, but is 

 sometimes smoothish. The color is whitish or a little bluish. 

 The males grow to the length of three or four inches, with a 



