ANIMAL I' AHA SITES 



29 



shape and are provided with a genital pore on each side and with 

 double sets of reproductive organs. The uterus forms numerous 

 diverticula, enclosing packets of 8 to 15 eggs. Distinguish in 

 mature segments the genital pore on each side, with cirrus, 

 cirrus pouch, vas deferens, vagina, ovary, vitelline glands, and 

 the diverticula of the uterus. The cysticercoid stage develops 

 in fleas and lice of the dog and cat. 



Diphyllobothrium latum (Linn) ( = Bothriocephalus of older 

 writers) is the broad or fish tapeworm of man and various 

 carnivores. It is the largest of the tapeworms of man, since 



vitelline gland 



y/lell'ne duct 

 seminal receptat/e 



ovary 

 ~A7ehli's' aland 



Fig. 10. — Diagram of a mature proglottis of Diphyllobothrium. 



and Mandoul.) 



{After Verdun 



it may attain a length of 15 meters or even more and possess 

 from 3,000 to 4,000 proglottides. The ovoid head has two 

 elongate attachment grooves, or bothridia. The proglottides 

 are much broader than long and in their center is the uterus, 

 in a rosette-like coil (Fig. 10). In the fresh specimen this appears 

 as a dark median area which readily distinguishes the worm 

 from the large tsenias of man. The genital pore is situated 

 in the mid-ventral line instead of laterally, and slightly farther 

 back is a second opening through which the eggs are laid. The 

 paired ovary is at the posterior end and the vitelline glands at 

 the sides of the proglottides. The eggs are large, elliptical, 

 brown, and provided with a cap, or operculum. 



The fish tapeworm of man is one of the few cestodes known 

 to require three hosts for its life cycle. From the egg there 

 emerges a free-swimming ciliated embryo known as a coracidium, 

 which after a short time enters one of various minute Copepod 



