158 



PRACTICAL PARASITOLOGY 



position of the testes, however, is very characteristic ; in each segment 

 they occupy a position in the narrow marginal fields external to the 

 excretory canals, leaving the wide middle field entirely free. The 

 latter is occupied by the numerous bullate diverticula of the uterus, 

 which is placed transversely. The eggs, six to ten of which lie in 

 each diverticulum, soon lose their shells, leaving the oncospheres 

 surrounded by a simple chitinous envelope without appendage. 1 



Another group of the Taeniidse, members of which infest the 

 domestic mammals, is the genus Dipylidium, E. Lkt., which is 

 described above. Tseniae having the genital pores upon the flat 

 surface, with sac-shaped uterus and unarmed head, are occasionally 



FIG. 79. Two mature proglottides of Mo- 

 niezia expansa. Id., Interproglottidal glands ; 

 above these are the testes ; at the sides, the 

 female sexual glands may be seen. 



FIG. 80. Egg of Moniezia expansa, 

 very much magnified. (After Moniez.) 

 In the centre, the oncospheres, sur- 

 rounded by the pyriform apparatus, are 

 seen. 



met with in the cat and dog, though they are more frequent in the 

 fox. These parasites belong to the genus Mesocestoides, Vaill. 

 (= Ptychophysa Hamann). 2 Dibothriocephalus latus is found in 

 dogs in localities only where this worm is prevalent, and it is 

 encountered even less frequently in the cat. Of still rarer occur- 

 rence in the latter host is Bothriocephalus felis, a much smaller 

 species of parasite. According to Krabbe, dogs in Iceland harbour 

 Bothriocephalinidae of species which are unknown to us. 



The numerous Cestodes harboured by our domestic poultry belong, 



1 C. W. Stiles and A. Hassall, " A Eevis. of the Adult Cestodes of Cattle, Sheep, 

 and Allied Animals " (United States Department of Agriculture, Bureau of Animal 

 Industry, Bull. No. 7, Washington, 1893). 



2 F. Zschokke, " Zool. Anz.". vol. viii, 1885, p. 380, u.l.c., Geneve, 1888 ; 0. 

 Hamann, Z. f. iviss. Zool., vol. xlii, 1885, p. 718. 



