STUDIES ON AVIAN H^MOPEtOTOZOA. 713 



above to the undoubted indications I have obtained that a 

 trypanosome of the little owl undergoes developmental phases 

 in Culex pipiens. There is^ therefore, no reason whatever 

 to doubt any longer that some, at all events, of the flagellate 

 phases described by Schaudinn in mosquitoes which, had fed 

 on infected birds were also actually phases of Trypanosoma 

 noctuas. Moreover, in regard to Crithidia fasciculata 

 itself, the type-species of that unfortunate genus, no one has 

 yet shown that it is solely an insectan parasite. In first 

 describing it, Leger very wisely admitted the possibility that 

 it was only a phase of a vertebrate trypanosome, and this 

 still remains the most logical assumption with regard to it. 



Similarly with regard to crithidial forms in other blood- 

 sucking insects, e.g. C. tabani, Patton (18), 0. melo- 

 phagia, Swingle (32), etc., by far the most likely and 

 reasonable view is that these parasites are merely the trypano- 

 monad forms of a trypanosome.^ One or two cases have 

 been described, howevei', of the occurrence of crithidial 

 forms iia what are alleged to be non-sanguivorous insects, 

 e.g. 0. gerridis from Gerris fossarum, Patton (16); 

 such parasites may apparently be regarded as true C r i t h i d i a, 

 by which we may understand flagellates that have developed 

 a trypanomonad condition, but which are restricted to an 

 invertebrate host. 



Two or three parasites have recently been described, and, 

 moreover, from non-biting insects, which have been regarded 

 as " trypanosomes." They are Trypanosoma drosophilse, 

 Chatton and Alilaire (3), and two peculiar herpetomonad 

 forms termed Leptomonas mirabiiis, from Pycnosoma 

 putorum and L. mesnili, from species of Luculius, which 



' As regards C . ni e 1 o p h a g i a , I have quite recently obtained evidence 

 which makes tliis almost certain. After prolonged examination of the 

 blood of a sheep on which were " keds " infected with this parasite, I 

 had the good fortune to find a typical, active trypanosome. This is 

 the first occasion, so far as I know, of a (natural) trypanosome having 

 been found in this domestic animal. There can l)e little or no doubt 

 that the " Crithidia meloj)hagia " is simply a developmental phase 

 of this sheep-trypanosome in its alternate, insectan host. 



