l!"ii| Kofoid-Mc('\iUftcli : Trupaimsoma friafonwf 117 



from the rat's nest four days prior to the examination, as merozoites, 

 or stomach phases resulting from multiple fission. Tlie stomach of 

 this bug contained digesting blood and the trypanosomes were of a 

 smaller, narrower, often straighter type (compare figs. 1-S with 9-12). 

 These dififerences are of the same general type of change as that found 

 by Minchin and Thomson (1915, pi. 45) in T. lewisi in the flea after 

 intracellular multiple fission. 



The merozoite (pi. 14, figs. 9-12) is characterized by shorter body 

 (less than 20^), less diameter ( not over 2/^), more elongate, narrower 

 nucleus, more rigid body (note more flowing curves), and more at- 

 tenuate proportions. It does not seem advisable to use the term 

 "crithidiomorphic" forms for these, as Minchin and Thomson (1915) 

 have done in this phase of T. lewisi, since the parabasal body and 

 blepharoplast in the merozoites of T. triatomae are characteristically 

 located at the extreme posterior tip of the body. 



III. The Crithidi.vl Ph.vse 



We find in our material a very characteristic occurrence of large 

 crithidial forms in ihr stomach (pi. 14, figs. 13-19, pi. 15, figs. 20-28), 

 while those of the rectum (pi. 15, figs. 29^7) are on the whole in the 

 matei'ial we have examined distinctly smaller. 



These size distinctions raise the question whether or not the cri- 

 thidial phase in Trypanosoma, triatomae may not play a larger part 

 than in T. lewisi, and at least suggests the possibility that it may arise 

 regularly in the stomach rather than in the rectiim. Minchin and 

 Thomson (1915) explain the presence of crithidial forms in the 

 stomach in the flea as due to the backward migration of these stages 

 from the rectum after transformation therein from the trypanosome 

 phase. 



Our grounds for suggesting the possibility of the initial normal 

 development of crithidial stages in the stomach of Triatoma are (1) 

 their abundance, (2) their larger size generally in the stomach than 

 in the rectum, and (3) the occurrence of rolled-up stages, which in the 

 trypanosome phase of T. lewisi in the flea are premonitory of the 

 impending entrance of the parasite into the epithelial cell for mul- 

 tiple fission. Let us now consider these stomach phases of the cri- 

 thidial forms of T. triatomae. 



1. Transition forms. — When ingested with blood the organism is 

 a typical trypanosome with the parabasal posterior to the nucleus 



