234 



BIOLOGY OF THE PROTOZOA 



pass with the ingested food into the stomach (mid-gut) of the insect. 

 In this part they multiply actively in a peculiar manner, not as yet 

 described in the case of any other trypanosome in its invertebrate 

 host; they penetrate into the cells of the epithelium, and in that 

 situation they grow to a very large size, retaining their flagellum 



Fig. 122. — Trypanosoma lewisi. Cycle in the rat-flea Ceratophyllus fasciatus. 

 1, 2, blood trypanosomes entering the stomach; 3, 4, entering epithelial cells; 6-10, 

 intracellular somatella formation; 11, 12, adult trypanosomes leaving cell; N, young 

 trypanosomes repeating intracellular phase; C, Crithidial forms; H, haptomonads 

 reproducing by division. (After Minchin and Thompson.) 



and undulating membrane, and exhibiting active metabolic changes 

 in the form of the body, which in early stages of the growth is 

 doubled on itself in the hinder region, thus becoming pear-shaped 

 or like a tadpole in form, but later is more block-like or rounded. 

 During growth the nuclei multiply, and the body when full-grown 

 approaches a spherical form, and becomes divided up within its 



