WOUMS. 



201 



Wlicnt-e ciiiiie these Tcunia cucumerincB ' I knew not, and I frankly owned it It) 

 members of the commission who proposed the question to me. This, however, did 

 not prevent my being greatly puzzled by the presence of this worm, of whose origin I 

 had no idea. Now we know whence they came. An acaris, tlie Trichodectes, lives in 

 the hair of young dogs, and harbors the scolex (larva) of this cestode. The dog, by 

 licking its own hair, grows infested, like the horse, which in a similar manner intro- 

 duces the gad-fly, and, though it has taken no other nourishment, harbors its own 

 epizoaria." 



Sheej) are afflicted by a disease known as the " gid," or " staggers." Tiie animal goes 

 round and round ; its jjower to walk straight ahead is lost. This curious effect is pro- 

 duced by the presence of a hydatid, a many-headed larva of a tape-worm ; the larva has 

 long been known under the name of Cmnurus cerebralis, and is the cause of a mortal 

 disease but too well known to the farmer. The pressure and irritation caused by the 

 hydatid produces inflammation and degeneration in the surrounding tissues. For a 

 long time the further metamorphoses of this species remained undiscovered, but it 

 has since been ascertaijied that the mature stage is reached in the dog. 



The second family of Cestodes, the Tseniadte being the first, are the Botiiuiockpiia- 

 LiD^, distinguished by having only two weak and shallow suckers on the head, lloth- 

 riocep/ialus latus is the largest of internal human parasites, specimens occurring 

 twenty-five and thirty feet in length. Its history has not yet been satisfactorily 

 worked out, but it is known that the embryo first enters the water, and probably 

 jiasses its larva life in a fish. 



We will not attempt to describe all the types which mark off the families of tape- 

 worms, but we can at least indicate the great variety of a]i]iearances among the s])e- 

 cies. This is especially noticeable in the Xa^q- 

 worms of birds and reptiles, whose jaredaceous 

 Iial)its lead them to engulph many aquatic ani- 

 mals laden with larval ])lathelminths, which reach 

 their full development in the bird or lizard. The 

 accompanying wood-cut shows two forms. A, 

 Tmnia filum^ which was described long ago Ijy 

 Goeze ; the head is scarce over a millimeter in 

 width, and is furnished with a crown of ten small 

 hooks ; the eysticercus stage is unknown, but the 

 adult is found in the intestine of ^colopax. Tot- 

 anus, and Trill (/a. B represents the very singu- 

 lar Opliryocotiile proteus, originally discovered by 

 Dr. Friis ; the head ends in a large fan-shaped 

 cupula, and bears six distinct festoon-like suckers ; 

 it grows to a length ordinarily of four inches ; it 

 is found in the intestine of certain sandpipers and 

 ]ilovers. There is a rich field of interesting study 

 oi>en to a nat\n-alist who will turn his attention to the parasitic plathelniinths of our 

 water and shore birds. Another very remarkable genus has been found in Yaranii,s, a 

 genus of lizards, and recently described by Prof. Perrier of Paris, and were obtained 

 by M. Vallee from the lizards kept at the Jardin des Plantes. The tape-worm in 

 question has been named D^Uhiersia, after Prof. Lacaze-Duthiers ; it is distinguished 

 by the enormous development of the lateral suckers, which form two large cups with 



Fig. 185. —.-l, Tan'mfilu 

 protett 



B, Oj/hri/oco/t/fe 



