A. Porter 
249 
forms are inadequate and unsatisfactory, for they are all about the same 
length and merely illustrate, as Mr Dunkerly himself states: “ the 
varying position of the kinetonucleus and the presence of an undulating 
membi’ane.” 
How can dogmatic statements based on the knowledge of part only 
of the life-cycle of a Leptomonas be regarded as hnally settling the 
question of the validity or otherwise of a totally different genus, 
Grithidial It is a presumption to set forth such statements on such 
hopelessly inadequate evidence. 
With regard to the second part of the statement that Grithidia are 
probably stages of trypanosomes, no definite evidence in support of 
this statement is forthcoming. I can find nowhere that the conversion 
of a trypanosome into a true Grithidia and of a true Grithidia into 
a veritable trypanosome have been witnessed in the living organisms. 
Herpetomonas and Grithidia, considering their definition, have not 
necessarily anything to do with trypanosomes. To introduce the 
trypanosomes into the discussion of the genera Herpetomonas and 
Grithidia is merely and immediately to confuse the issue. Hypotheses 
as to whether a flagellate is primarily a parasite of an insect or of a 
vertebrate are purely speculative and can only be treated as such. 
The opinion of L. Leger in respect to the position of the trypanosomes, 
is, however, of interest:—“ Les trypanosomes du sang, ne representent 
qu’une adaptation partielle et secondaire d’un parasite primitivement 
intestinal ou enterocoelomique d’lnvertebre.” Having regard to this 
statement, the discussion of insect flagellates fiom the trypanosome 
point of view" is commencing at the wrong end and so working 
backwards. 
I think that there is little doubt that Mr Dunkerly has found 
a Herpetomonad in Homalomyia canicularis, belonging to the Lepto¬ 
monas and leptotrypanosomes of Chatton and A. Leger. However, 
Mr Dunkerly has not got a Grithidia, for as Chatton and Leger say, 
“ Elies [leptotrypanosomes] approchent de stade Grithidia sans toute- 
fois atteindre.” Leptotrypanosomes have the flagellum attached to the 
body, there is no membrane and the blepharoplast is posterior, conjoined 
characters which do not occur in Grithidia. However, the observations 
of Miss Mackinnon (1910) on a Herpetomonas from a Homalomyia are 
most instructive. Miss Mackinnon finds Herpetomonas therein which 
often exhibit the peculiarity of the flagellum being bent back and 
“sticking” to the body. May not this account for the phenomenon seen 
by Chatton and by Dunkerly ? It is strange that Mr Dunkerly, although 
