1919] McCulloch: Life Cycle of Crithidia and Trypanosoma 157 



at the bases of the flagella. Later stages showed only flagella among 

 the zooids. This additional evidence from the two smears at once 

 suggested the work of Moore and Breinl (1907), in which " latent 

 bodies ' ' were described in the life cycle of a haemoflagellate, Trypano- 

 soma gambiense. 



According to these investigators T. gambiense in the blood of a 

 vertebrate host formed latent bodies in the nuclear region, under 

 certain conditions. These latent bodies are pictured and described 

 as being small nucleated structures having a nuclear membrane and a 

 single mass of chromatin in the center. The exact method of the 

 formation of the bodies in the nucleus or from the nucleus is not 

 clear, since none of the early stages in the formation of the latent 

 bodies are figured or described in detail. Apparently only the results 

 of an endogenous process in the life cycle of T. gambiense were ob- 

 served by these investigators. The final stages of the process in the 

 life cycle of T. gambiense are the presence of large, degenerating try- 

 panosomes with minute, nucleated latent bodies in the nuclear area. 

 The flagellum, kinetonucleus, or parabasal body and cytoplasm are in 

 various stages of degeneration. Their figures of the latent bodies 

 (Moore and Breinl, 1907) should be compared with figure 23 of this 

 paper. 



The latent bodies in the life cycle of Trypanosoma gambiense and 

 the endogenous zooids of the life cycle of Crithidia euryophthalmi are 

 not the only instances of an endogenous budding in the life cycle of 

 the Protomonadina (Trypanosoma, Crithidia, Herpetomonas, Lepto- 

 monas). Minchin and Thomson (1915) searched for evidence of an 

 endogenous budding in the life cycle of T. lewisi but failed to find any 

 indications of the process. However, in the life cycle of Leptomonas 

 pattoni, one of the so-called natural flagellates frequently found in 

 the digestive tract of the flea, they found several crithidial-like flagel- 

 lates containing a nucleus and an endogenous bud. These authors 

 suggested that the endogenous buds found therein were doubtless com- 

 parable to the latent bodies of Moore and Breinl. 



The early stages of the endogenous, or internal budding of Crith- 

 idia euryophthalmi are shown in figures 11 and 12, plate 2. In figure 

 11 there is a relatively short flagellate undergoing multiple fission in 

 this way. The nucleus has budded off two circular, nucleus-like buds, 

 each showing a chromatin-encrusted nuclear membrane. The para- 

 basal body and the flagellum of this flagellate are still intact and have 

 no indications of binary fission. Somewhat similar to this flagellate 



