THE TAPEWORMS 61 



EXERCISE 34 



THE TAPEWORMS A SYSTEMATIC STUDY 



PHYLUM PLATYHELMINTHES, CLASS CESTODA 



A. Characteristics of Cestoda. These flat-worms consist usu- 

 ally, in the adult form, of a small globular head or scolex, and 

 a chain of segments called proglottides. In the adult stage they 

 are parasitic in vertebrate animals, having the larval (bladder 

 worm) stage in a secondary host, frequently invertebrate. 



B. Examine specimens of the following species as far as avail- 

 able included in the two most important tapeworm families. 

 The following list is only partial, and is meant to give the student 

 merely a hint as to classification. Take notes on the specimens, 

 with reference to characteristics. 



a. Family Bothriocephalida. "Head provided with two 

 groove- or slit-like suckers; rostellum wanting; uterus with 

 special pore; genital pores generally (possibly always) dorsal or 

 ventral." (Stiles.) 



i. Genus Bothriocephalus, two elongate groove-like suckers 

 present; the sexual pore opens in the mid- ventral region. 



E. g. Bothriocephalus latus, the fish tapeworm of man, also 

 found in dogs and other animals experimentally. May reach a 

 length of 20 to 30 feet, with some 4000 proglottides. The 

 middle proglottides are about three times as broad as long. The 

 larva is a plerocercoid inhabiting the muscular system of certain 

 fresh water fishes. 



b. Family Taniida, "Head with four cup-shaped suckers; 

 rostellum present but not always evident; uterine pore wanting; 

 genital pores generally marginal; body always segmented." 

 (Stiles.) 



i. Genus Tania, scolex with a rostellum usually provided 

 with hooks; mature proglottides longer than broad; genital 



