AVES 435 



PART I (AVES). 



A prodigious number of entozoa are known to infest birds. 

 So far from birds being less victimised than mammals, the 

 contrary is the case. Every now and then avian epizootics, 

 due to parasites, sweep off hundreds of these attractive hosts, 

 and in some cases even nestlings are not secure from entozoal 

 invasion. It might be supposed that predacious birds would 

 be more liable to invasion than the graminivorous species. 

 Such is not the case. The eagles, hawks, vultures, and owls 

 certainly harbor a great variety of helminths, but as much may 

 be said of the grain-feeding game birds, and still more of the 

 water birds. Pheasants and land-fowl, grouse and partridges, 

 are largely infested ; whilst, of water-fowl, herons and plovers, 

 rails and snipe, ducks and geese, cormorants and divers, gulls 

 and awks, play the r61e of host to a practically infinite variety 

 of parasitic guests. The presence of the worm-guests does not 

 imply any previously diseased condition of the host. Shoot any 

 water bird, say an oyster catcher (Hoematopus), or, still better, 

 a grebe (Podiceps), and then carefully examine its intestinal 

 contents. You will probably find in its interior flukes and 

 round worms, tapeworms and Echinorhynchi. Capture and 

 examine a frog or a salamander. The result is the same, except 

 that the cestodes would probably be absent. As for fishes, if 

 entozoa be a proof of cachexia, then it follows that the normal 

 condition of all piscine hosts is a diseased state. Examine any 

 tolerably well-grown salmon, trout, pike, perch, roach, chub, 

 carp, or barbel, and probably any one of them will contain at 

 least three different kinds of parasites, each of which will be 

 present in more or less considerable numbers. From what is 

 stated above it would be obviously futile to attempt even an 

 enumeration of the species of avian entozoa a remark which 

 applies almost equally to the other groups of hosts that remain 

 for consideration. Confining our attention to a few of the more 

 noteworthy facts, I may observe that we have no very trustworthy 

 data respecting the power for mischief possessed by flukes. 

 From what we know of their destructiveness in man and certain 

 other mammals, it would be hazardous to pronounce them 

 harmless. Scientifically, they furnish particulars of great 

 interest. One of the most striking facts of recent study relates 

 to Zeller's discovery that the little cercariae (G. exfoliata) 

 which are contained in a peculiar sporocyst (Leucochloridium 



