THE H^MOFLAGELLATES. 249 



gametes^ but becomes itself a single one, in the same way 

 that a female form becomes a megagamete after maturation. 

 The body diminishes in size, and the nucleus (tropho- 

 nucleus), becomes elongated and band-like (fig. 36 a) ; also 

 the cytoplasm stains differently from that of a female gamete. 

 Hence, when fully formed, the two kinds of sexual element 

 are readily distinguishable, although there is not any pro- 

 nounced dissimilarity in type. Actual conjugation stages 

 are shown in fig. 36 b and C; and it is, in the writer's 



Fig. 36. — a, microgamete of T. lewisi ; b and c, stages in con- 

 jugation ; D, zygote (ookinete). (After Prowazek.) 



opinion, a point of great importance that the gametes come 

 into contact by their non-flagellate, kinetonuclear ends. 

 The zygote becomes an ookinete (fig. 36 d), quite similar in 

 constitution to those of Trypanomorpha and Trypano- 

 soma ziemanni; and this gives rise to a single Trypano- 

 some by the separation of kinetonucleus and locomotor appa- 

 ratus, also in the same manner as in those parasites. 



Prowazek has also endeavoured to ascertain more of the life-cycle of 

 T. brucii. He was unable, however, to obtain the Tsetse-fly (Glossina 

 inorsitans) in which, as he remarks, the sexual jihases normally occur, and 

 only very rarely were maturation. processes, comparable with those described 

 for T. lewisi, to be seen in the blood. In one case, where the parasites 

 were in a guinea-pig which had just died, he was able to observe what was 

 undoubtedly an actual conjugation, although probably not altogether typi- 

 cal (cf. footnote ^ p. 246). 



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