THE HAEMOFLAGELLATES 243 



stages in a Herpetomonas of Culex pipiens, whose life-cycle would 

 seem in some respects to conform to the scheme suggested by Ross. 

 In its monadine, determinative form, the parasite appears to be a 

 typical Herpetomonas, with no indications of an undulating membrane. 

 All the phases observed, Patton states, exhibit great similarity with 

 those of Piroplasma donovani (see pp. 256 et seq.). Here it may be 

 pointed out that in the larvae the parasites resembled the Leishman- 

 Donovan bodies as they occur in human tissues ; in the nymphs, 

 stages corresponding to the developmental forms of the Leishman- 

 Douovan bodies (in cultures, or in the bed-bug), i.e. pear-shaped forms 

 with flagella, were numerous ; while in adult mosquitoes (mid- and 

 hind-gut) there were fully developed Herpetomonad forms. Patton 

 thinks these are passed out into the water, and in some guise or other 

 ingested by the larvae, the cycle thus beginning again. (He has 

 privately informed the writer that the parasites may encyst in the 

 rectum, and be thus passed out to the exterior, to give rise to the 

 small round forms in the larva.) Patton also notes the occurrence 

 of a Herpetomonad, which has an obvious undulating membrane, 

 and which possesses similar rounded aflagellar forms, in a water- 

 bug. The author concludes by regarding these two parasites as 

 limited to their Insectan hosts. 



In endeavouring to draw some general conclusions from the 

 above opposing ideas, we are, it seems to the writer, greatly helped 

 by comparing what is known in the case of other groups of Trypano- 

 somes. In the first place, as regards those met with in Tsetse-flies, 

 some of which, at any rate, were formerly considered to be solely 

 fly-parasites, there appears to be no escape from the conclusion that, 

 on the contrary, all the forms are blood-parasites. In our opinion 

 the utmost weight is to be attached to this conclusion. In addition, 

 we have the Trypanosomes of leeches, which are generally agreed to 

 belong to different Piscine forms. On these grounds alone, then, it 

 appears justifiable to suppose that Avian -Trypanosomes are to be 

 found in mosquitoes, and not at all improbable that some at least 

 of the phases so clearly described by Schaudinn from mosquitoes 

 which had fed on infected owls, did indeed appertain to Trypano- 

 morpha noduae. 



Again, to consider the subject from the Insectan standpoint, so 

 far as the writer can see, Novy and his colleagues have by no 

 means proved that their Flagellates in wild mosquitoes are not, in 

 some cases at any rate, phases of Trypanosomes of birds (or other 

 Vertebrates). For instance, the Trypaiwsoma (Herpetomonas) culicis 

 described by these authors with various forms of which they 

 compare certain phases of Trypanomorplia is quite as probably a 

 blood-parasite as a purely Insectan form ; indeed, the possibility of 

 this being so is admitted by its describers. Moreover, they remark 

 on the resemblance between the genera Herpetomonas, Crithidia, and 



