THE HAEMOFLAGELLATES 227 



whole trend of research pointed at the time to a very complex 

 life-cycle of the Haemoflagellates and to a close connection with 

 the Haemosporidia. Since then, however, owing in a great^ 

 measure to the work of Xovy and M'Neal on the Trypanosomes of 

 birds (62) and of mosquitoes (G3), the results obtained by 

 Schaudinn have become, to a large extent, discredited ; these 

 authors maintaining that they are capable of a quite different 

 interpretation. Moreover, influenced by their work on Insectan 

 Flagellates, Novy and his colleagues have gone to the other 

 extreme and expressed their belief not merely that Haemorlagellates 

 and Haemosporidia are entirely distinct, but also that the Trypano- 

 somes of Vertebrates do not undergo any true development or part 

 of their life-cycle in the Insectan host. This latter view, at all 

 events, is, we think, shown to be incorrect by the most recent 

 research, which, as above mentioned, seems all in favour of an 

 alternate, Invertebrate host, one of the most important indications 

 being with regard to the specificity of the latter a point of the 

 utmost consequence in its bearing upon investigations of this kind. 

 Leaving aside for the moment a consideration of Schaudinn's 

 celebrated memoir, it will be best to give first a brief account of 

 the results obtained in this connection by different prominent 

 researchers, to other aspects of whose work reference has been 

 previously made. 



Dealing first with Trypanosomes of cold-blooded Vertebrates, 

 the earliest important observations are those of Leger (<">0), relating 

 to Ti'ypiuwpliisiiut Tcu'inni and Ti'>ip<.iiwsuina bitrl/aftilae of the loach. 

 L('-ger distinguishes ordinary ('indifferent") ami larger, more 

 granular (probably female) forms of the Ti'yptimyla&ma in the 

 blood of the fish. "When a leech (/A'y/mVryWx sp.) was allowed to 

 suck blood containing only these parasites, which thereupon passed 

 into its stomach, the indifferent forms degenerated and perished, 

 while the female ones became massive and showed nuclear changes, 

 preparatory, Lrger thinks, to a sexual process. At any rate, after 

 .some days, the intestine of the leech contained numerous little 

 narrow Trypanoplasms, of which some, very filiform, perhaps 

 represented male forms, while others possessed a kind of beak or 

 rostrum in place of the anterior flagelluin, which made them 

 resemble Trypanosomes. The development of Tri/panosoma bar- 

 batulae in another leech (Piscicoht) showed a certain amount of 

 agreement with that described by Schaudinn in the case of his 

 Avian Trypanosome in the gnat (Culex). Eighteen hours after 

 the leech had fed on blood containing exclusively T. barbatalae, 

 pyriform bodies lacking a flagellum (" ookinetes ") were found in 

 the intestinal contents. Some of these had a single large nucleus 

 (i.e. a compound nucleus) ; others had two nuclei, one smaller than 



