316 PARASITES OF ANIMALS 



Myoxus dry as, and M. muscardinus. The jerboas (DipodicUf), 

 in common with the hamster and several species of true mice, 

 are apt to be infested by Ascaris tetraptera ; and a small 

 nematoid, apparently immature, was noticed by Otto in the 

 intestines and in the abdominal walls and cavity of Dipus 

 tetradaciylus. Mice, properly so called, are largely infested, 

 as is also the hamster (Oricetus vulgaris), which I include in the 

 Muridce. In addition to the parasites already mentioned, the 

 hamster is infested by Tania straminea. Along with examples 

 of this tapeworm I have received from Dr Murie some acepha- 

 locysts found in a hamster which died at the Zoological Gardens. 

 Flukes exist in the long-tailed field-mouse (Distoma vitta and 

 D. recurvum), but I have not seen any in our common mice and 

 rats. However, Dujardin describes a distome (D. spiculator) 

 in the brown rat (Mus decumamis). One of the tapeworms 

 observed in the mouse (M. musculus) is Tania pusilla, also found 

 in the rat (M. rattus) and long-tailed field-mouse. The house- 

 mouse likewise harbors T. microstoma and T. leptocephala ; and 

 an immature cestode has also been seen in the abdomen, probably 

 a species of Ligula. Various species of rat also harbor T. 

 diminuta. In regard to the round worms one of the most 

 common species is Ascaris oxyura. This not only occurs in 

 rats and mice, but also in voles, water-rats, and many other 

 rodents. The rodents' whip worm (Trichocephalus nodosus) is 

 yet more common in the lemmings, rats, voles, and mice; 

 another species (T. unguiculatus) , taking its place in hares and 

 rabbits, and yet another (T. affinis) in the porcupine. Another 

 nematoid, very common in mice, is Spiroptera obtusa, occupying 

 the stomach. I have seen a mouse with its abdomen so dis- 

 tended by their presence that the animal could scarcely run 

 along the pathway where it was killed by being trod upon. 

 According to Marchi, the young of this entozoon dwell in the 

 fat surrounding the alimentary canal of the larva of an insect 

 (Tenebrio molitor). When noticing the parasites of the cat I 

 referred to Leuckart's interesting discovery of the relations 

 subsisting between the adult Olulanus tricuspis, found in the 

 stomach walls of that feline, and the immature encysted worms, 

 found not only as wanderers in the cat itself but also in the 

 muscles of mice. The olulanised mouse is thus an intermediate 

 host. Rats and mice also play the part of intermediary bearers 

 in the case of two other species of entozoa, namely, Trichina 

 *>i rails and Tania crassicollis, the tsenioid scolex or larval 



