WORMS. 



201 



Whence came these Tcenia cucumerincef I knew not, and I frankly owned it to 

 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, the IHchodectes, 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 

 epizoai'ia." 



Sheep are aflOiicted by a disease known as the " gid," or " staggers." The animal goes 

 round and round ; its power 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 Caenurus 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 ascertained that the mature stage is reached in the dog. 



The second family of Cestodes, the Taeniadse being the first, are the Botheiocepha- 

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

 riocephalus lotus 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 

 passes 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 appearances among the spe- 

 cies. This is especially noticeable in the tape- 

 worms of birds and reptiles, whose predaceous 

 habits lead them to engulph many aquatic ani- 

 mals laden with larval plathelminths, which reach 

 their full development in the bird or lizard. The 

 accompanying wood-cut shows two forms. A, 

 Tcenia filum, which was described long ago by 

 Goeze ; the head is scarce over a millimeter in 

 width, and is furnished with a crown of ten small 

 hooks ; the cysticercus stage is unknown, but the 

 adult is found in the intestine of Scolopax, Tot- 

 anus, and Tringa. B represents the very singu- 

 lar Ophryocotyle 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 

 plovers. There is a rich field of interesting study 

 open to a naturalist who will turn his attention to the parasitic plathelminths of our 

 water and shore birds. Another very remarkable genus has been found in Varanus, 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 Ditthiersia, after Prof. Lacaze-Duthiers ; it is distinguished 

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



Fig. 185. — -^, Taniafilum; B, Ophryocotyle 

 proteus. 



