HOST-PARASITE SPECIFICITY IN THE GENUS GIARDIA 149 



reported from several cold-blooded animals, including tadpoles of 

 frogs. The incidence of infection in tadpoles seems to be high and 

 hence this material is easy to obtain. Giardias of cold-blooded ani- 

 mals may be more easily cultivated than those of warm-blooded 

 animals and hence experiments with Giardia agilis are indicated. 



Fig. 14. — Giardias from man and lower animals. Diagrams showing the 

 specific differences between giardias living in different species of animals, 

 a, G. lamblia from man. b, G. duodenalis from the rabbit, c, G. muris from 

 rats and mice, d, G. agilis from frog tadpoles, e, G. canis from the dog. f, G. 

 microti from meadow mice, g, G. cavice from the guinea-pig. X 2800. (a, c, f, 

 after Simon; b, d, e, g, after Hegner.) 



Until it is possible to cultivate giardias many problems will have 

 to remain unsolved. Reference may be made here to the fact that 

 the first definite success in the cultivation of an Endanwcha was 

 that of Barret and Smith (1923) who succeeded in cultivating 

 E. barrcti of a cold-blooded animal, the turtle, and to the great 

 progress that has been made in our knowledge of Endamocha his- 



