198 PARASITES IN THE INTESTINES 



in the posterior part of the segment. The cyst form and 

 intermediate hosts are unknown. 



T sendee in the Intestines of Birds. In the intestines of the 

 fowl, nine species of cestodes have been found eight tsenia 

 and one bothriocephalus. The tsenise are difficult to distin- 

 guish from one another, and as they are rare, little work has 

 been done to establish their complete history. Outbreaks do 

 occur, however, in which so many fowls are infested as to 

 amount to an epizootic tseniasis. 



(a) Choanotcenia infundibuliformis, length 20 to 130 mm., 

 armed and supplied with suckers. Intermediate host said to 

 be the common house fly. 



(6) Dicranotcenia sphenoides, length 2 mm., head armed 

 and supplied w r ith suckers. Intermediate host the earth- 

 worm. 



(c) Davainea proglottina, length 1.0-1.5 mm., head armed, 

 and supplied with suckers. The segments of this taenia are 

 cast off as soon as mature. They continue to live and develop, 

 greatly increasing in length. Intermediate hosts are various 

 species of mollusca. 



(d) Davainea cesticillus, length 9 to 45 mm., head unarmed. 

 Intermediate host unknown. 



(e) Davainea echinobothrida, length 50 to 100 mm., head 

 has suckers and is armed. Intermediate host unknown. 



(/) Davainea tetragona, length 25-100 mm., head has 

 suckers and armed. Intermediate host unknown. Very little 

 is known of the other species. 



(</) Tcenia cantaniani, the only tsenia found in turkeys. 

 It is 14 mm. long, head unarmed, but provided with suckers, 

 and has no neck. Life history unknown. 



(h) Davainea crassula very rarely infests pigeons. Length 

 30 to 40 cm., breadth 4 mm., head armed with double crown 

 of 60 hooks. First segment short, posterior ones long, genital 

 pores unilateral. Ova very large, ovoid, 28 microns long, 

 and arranged in groups. 



Pathology. TflenicT are extremely frequent in dogs, but the 

 various species are not equally distributed, and the variation 

 seems to pertain to different countries and also to the differ- 

 ent sections of the country. The frequency of tsenia is also 



