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A CRITICAL REVIEW OF THE RELATION OF BLOOD¬ 
SUCKING INVERTEBRATES TO THE LIFE CYCLES 
OF THE TRYPANOSOMES OF VERTEBRATES, WITH 
A NOTE ON THE OCCURRENCE OF A SPECIES OF 
CRITHIDIA, C. CTENOPTHALMI, IN THE ALIMENTARY 
TRACT OF CTENOPTLIALMUS AGYRTES, HELLER. 
By Captain W. S. PATTON, M.B. Edin., I.M.S., 
and C. STRICKLAND, B. A. 
{From the Quick Laboratory , Cambridge.) 
It is now an established fact that a number of blood-suckiug 
arthropods and leeches are infected with flagellate organisms belonging 
to the genera Herpetomonas and Crithidia, and we believe that in more 
than one instance, these natural flagellates have been described as 
developmental forms of various trypanosomes which might be ingested 
by these sanguivora. As the whole question of the transmission of 
trypanosomes is intimately connected with these so-called developmental 
forms in invertebrate hosts, we propose reviewing in detail this important 
subject before recording our observations on the flagellate of Ctenopthal- 
mus agyrtes. 
It will be remembered that the late Dr Schaudinn (1901) was the 
first to give a detailed description of the life-cycle of a trypanosome 
( T. noctuae) in a blood-sucking invertebrate, Culex pipiens. Although 
he referred to the similarity between his developmental forms in the 
mosquito and Crithidia fasciculata of Leger (1902), he made no reference 
to the possibility of his mosquitoes being infected with similar flagellates. 
Novy (1907) and his collaborators have clearly shown that both Herpe- 
tomonas and Crithidia may occur in the same mosquito, and one of us 
(1907) has traced the development of Herpetomonas cidicis Novy from 
the larva of the mosquito through the nymph up to the adult insect, 
showing that even when mosquitoes are bred in the laboratory from 
larvae caught at large they may be infected with this flagellate. 
