346 



PROTOZOOLOGY 



slender forms appear in great numbers and these migrate back gradu- 

 ally towards proventriculus in which they become predominant 

 forms. They further migrate to the salivary glands and attach them- 



Fig. 142. The life-cycle of Trypanosoma lewisi in the flea, Ceratophyl- 

 lus fasciatus (Minchin and Thomson, modified), a, trypanosome from 

 rat's blood; b, individual after being in flea's stomach for a few hours; 

 o-l, stages in intracellular schizogony in stomach epithelium; m-r, two 

 ways in which rectal phase may arise from stomach forms in rectum; 

 s, rectal phase, showing various types; t, secondary infection of pylorus of 

 hind-gut, showing forms similar to those of rectum. 



