W. S. Patton and C. Strickland 
339 
which has a truncated anterior end, single flagellum and no undulating 
membrane. Figs. II and 12 are two flagellates of Herpetomonas 
muscae domesticae from the same fly; fig. 11 shows the appearance of 
the double flagellum, which we regard as the early stage in division, 
and fig. 12 represents an adult flagellate with a single flagellum. 
The Grithidia are closely allied to the Trypanosoma in that they 
possess a rudimentary undulating membrane, and in some species, 
particularly those occurring in ticks (fig. 9), the blepharoplast passes 
behind the nucleus; many of these forms however represent early 
division stages (unequal) and in the typical adult forms the blepharo¬ 
plast is never very far behind the nucleus. 
These flagellates have up to the present only been found in the 
alimentary tracts and malpighian tubes of arthropods and leeches, and 
it is a remarkable fact that the majority of known species occur in 
blood-sucking invertebrates. In another paper in this Journal (p. 314), 
Wenyon records a very interesting flagellate from the blood of Erythro- 
lamprus aesculapii ; this parasite is the first flagellate we know from 
the blood of a vertebrate which at once suggests a Grithidia rather 
than a true trypanosome. A glance at Wenyon’s figures will show that 
his flagellate differs considerably from the pathogenic trypanosomes of 
mammals. It is not at all unlike the flagellate from Haemaphysalis 
flava, which we believe is a Grithidia, both having attenuated posterior 
ends. It is impossible, however, to come to a definite conclusion 
regarding the exact position of the snake flagellate until more is known 
of its life-cycle. 
We would pass the same remark on Chatton and Alilaffe’s (1908) 
parasite from the malpighian tubes of Drosophila confusa which they 
call Trypanosoma drosophilae. It is dangerous to form a definite 
opinion as to the biological position of these insect flagellates on 
morphological grounds alone and we cannot too strongly draw attention 
to the fact, that a knowledge of the complete life-cycle of a protozoon is 
of tlie greatest value, for it is only then possible to form an adequate 
conception of any species and its relationships. We have pointed out 
above that in a certain stage in its life-history a Grithidia may be very 
like a young trypanosome, e.g. a short form of T. dimorphon. We 
would also like to draw attention to the great tendency there is at 
the present time of theorising on the origin of the trypanosomes and 
allied flagellates. Prowazek (1904, 1905), Brumpt (1908), Minchin 
(1908), Woodcock (1906), and others have each advanced a particular 
hypothesis of their own, and now we find Chatton and Alilaire (1908) 
