160 H. M. WOODCOCK. 



The main facts elucidated by this author's cpoch-niarkiiig- 

 research may be here stated. His description relates to two 

 distinct organisms, Trypanosoma (here called 'J'rypano - 

 morpha) nocture and Tj-ypanosoma ziemanni. The 

 latter Trypanosome is remarkable for the great resemblance 

 it offers in certain phases to the Bacterial parasites, possess- 

 ing the form of spiral threads, which constitute Ehrenberg's 

 genus Spirochgeta (allied to Spirillum).^ In both these 

 Haemoflagellates, the general plan of the life-cycle shows a 

 fundamental agreement. The gnat is a true host, and, 

 indeed, the principal or definitive one, since in it the sexual 

 process is undergone. During much of the time spent in 

 the blood of the bird, the parasites are attached to or pene- 

 trate into a blood-corpuscle, acquire a resting, "gregarini- 

 form " condition, and become, in fact, what have hitherto 

 been recognised as characteristic Hasmosporidia. The first- 

 named Trypanosome passes into a species of Halteridium, 

 the latter into a species of " Hgemamoeba/^ or " Leucocy- 

 tozoon." In other words these two HaBmosporidiau parasites 

 represent, respectively, only a transient phase in the life-cycle 

 of a particular Hgemoflagellate. 



Is a Similar "Alternation" Common to the 

 Majority of Try panosomes ? — These facts will serve 

 to indicate the great gap at present existing between our 

 knowledge of these two parasites of the owl and that of 

 most Try panosomes. In numy cases, indeed, almost the only 

 facts with regard to the life-cycle as yet known with cer- 

 tainty are that the parasites possess the faculty of "agglome- 

 ration," and that they multi])ly by longitudinal division. 

 There is, however, already a certain amount of evidence to 

 hand — and such evidence is rapidly increasing — Avhich tends 



dealing as it docs with revelations of sucli fundamental inijioitanco in tiie 

 study of the Hsematozoa, the corroboration leccntly alYorded b}' Serpent's 

 investigations (103) is higlily welcome. 



* So marked is this similarit}', indeed, tiiat Schaudinii was at first inclined 

 to consider this Trypanosome as exhibiting the typical cliaracters of a 

 Spirochacta (see Appendix). 



