116 
Haemoflagellates, etc. 
regard as stages in the development of vertebrate trypanosomes. We 
have shown above that the proof of this is wanting, and that there is also 
no proof to support the view that certain piscine trypanosomes undergo 
their development in the alimentary tracts of leeches. In all the 
instances we have quoted above, natural flagellates of the various 
sanguivora have not been excluded. We have no hesitation in saying 
that Herpetomonas culicis and Crithidia fasciculata, studied by Novy 
and his collaborators (1907), are in no way connected with an avian 
trypanosome. The American observers only studied the flagellate 
stages of the parasites in the mosquitoes and in test tubes. Had they 
however investigated their life cycles, as we have, we have no doubt that 
they would have found conclusive evidence to show that these flagellates 
are entirely limited to their insect hosts. We therefore cannot agree 
with Woodcock that any of these insect flagellates are connected with 
avian trypanosomes. It is quite premature to say that some of them 
may have developed a trypanosomal condition as an adaptation to the 
food of these sanguivorous insects, without being able to live in the blood 
of the vertebrate. The study of these flagellates in test tubes, and more 
especially partial descriptions of their life cycles, have largely contributed 
to the many erroneous views regarding their structure and relations. 
In his first article (1906) on the Haemoflagellates Woodcock ex¬ 
pressed the opinion that trypanosomes had originated from an ancestor 
parasitic in invertebrates. He however now believes that the-trypano¬ 
somes which have the vertebrate for their primary host are Heteromas- 
tigine forms, i.e. are derived from a bi-flagellate Bodo-like type; those 
parasitic in invertebrates he believes have originated from a Monadine 
ancestor. Woodcock states that in bringing forward this view he has 
been mainly influenced by the intestinal Trypanoplasmata, and by 
Minchin’s observations on Crithidia grayi. As so little is known of the 
intestinal trypanoplasmata, we think it is dangerous to draw important 
conclusions from our present knowledge of these forms. Are they true 
trypanoplasmata ? We do not know this for certain. We have pointed 
out above that Minchin’s hypothesis, regarding the life cycle of the 
flagellate of G. palpalis, is based on an incomplete study of its life 
history, as well as that of the tsetse fly, and that it is most improbable; 
in our opinion C. grayi is a true parasite of G. palpalis. Woodcock 
further thinks sufficient weight has not been attached to the fact that 
the majority of invertebrates, which harbour trypanosomes (according to 
our view crithidia), are blood-sucking insects. A large number of 
Rhynchota and flies which are not blood-suckers harbour typical Crithidia. 
