TRYPANOSOMES IN TSETSE-FLIES AND OTHER DIPTERA. 179 
IT am also unable to make head or tail of the “atypical” 
forms described by Castellani (13). I have never seen any- 
thing like them. I note that he states that they occur especi- 
ally in the last stages of disease. As my object was to trace 
the normal life-history of the parasite, | avoided as much as 
possible all material in which the parasites were likely to be 
influenced by a sickly condition of the host. Perhaps that 
accounts for the great discrepancy between my observations 
and those of these investigators with regard to the vacuolation 
of the trypanosome. 
(s) The Development of Trypanosoma gambiense 
in Glossina palpalis and other Diptera. 
My observations and experiments on the fate of TT’. gambi- 
ense in invertebrate hosts were carried out chiefly on Glos- 
sina palpalis, but I also made a few observations on the 
species of Stomoxys, common at Hntebbe, and on the 
two common Entebbe mosquitoes, one a species of Twnio- 
rhynchus, the other of Mansonia. 
The results obtained with Glossina palpalis were remark- 
ably uniform, and will be briefly summarised before entering 
into. full detail. The trypanosomes at first multiply in the 
digestive tract of the fly, and by twenty-four hours are found 
to be differentiated into two types, slender and stout, sharply 
‘distinct from one another, with no intermediate forms. 
The next day, that is, at about forty-eight hours, these two 
types are succeeded by a more uniform type, so far as struc- 
ture is concerned, but varying from slender to fairly stout, 
_with all possible transitions, and of considerable length. On 
the third day after infection trypanosomes are always to be 
found in the digestive tract, and are forms of great length, 
relatively, varying from slender to stout, sometimes appear- 
ing degenerate in structure and diminished in number, but in 
other cases numerous, active, and with no signs of degenera- 
tion. On the fourth day trypanosomes are very rarely to be 
found, and, if present, are very scanty in number and of large 
