TEEMATODA. 17 



expected, they are of remarkably frequent occurrence in the 

 alimentary canal of gulls, lierons, storks, cranes, plovers, ducks, 

 and other water birds. 



In Reptiles and Fishes. — Trematodes are not uncommon in the 

 cold-blooded reptiles generally, and they display considerable par- 

 tiahty for frogs and toads. In salamanders they occur less nume- 

 rously, and in the saurian, chelonian, and ophidian orders they are 

 comparatively unknown. In fishes the flukes are almost always 

 present, being particularly plentiful in the stickleback, minnow, 

 tench, perch, pope, bullhead, mackerel, trout, salmon, ling, burbot. 



Fig. 3. — Distoma COEONAEIUM, Cobhold. — From the alimentary canal of an Alligator {Alligator 

 Mississipiensis, Cuv.) X 8 diam. — Original. 



turbot, flounder, lump-fish, sander, and dorado; they are still 

 more abundant in the perch, pike, barbel, bream, eel, sole, sunfish, 

 and sturgeon. 



Number and Arrangement. — On the score of numbers no very 

 accurate estimate can be formed. Not long ago I made a special 

 investigation, partly with the view of determining this point, and 

 communicated the results of this inquiry to the Linnean Society. In 

 my " Synopsis of the Distomidse," I recognized 344 species of flukes, 

 126 of these belonging to fishes, 47 to reptiles, 108 to birds, 58 to 

 mammals, and 5 to the invertebrata. This fist, however, did not 

 embrace those leech-like forms of Trematoda (Tristoma, Poly stoma, 



