188 E. A. MINCHIN. 
To sum up, we may classify the ordinary type of T. grayi 
roughly into serpentine, vermiform, tadpole-like, young, and 
intermediate (i. e. growing) forms. ‘To these, however, must be 
added a sixth form, the significance of which is not at all clear 
to me. These are the round forms frequently present, and 
obviously connected with the young forms. It is easy, when 
round forms occur, to trace a series of transitional forms 
between them and the young forms, but whether round forms 
become young forms, or vice-versa, itis not so easy to deter- 
mine. A typical round form has a more or less spherical body, 
giving off a flagellum, which is entirely free except at its origin 
(fig. 136). Gray has figured a further development of the — 
round forms, in which the flagellum becomes wrapped round 
the body in such a way as to simulate a cyst or cuticle in 
optical section (P. R. 8., B78, Pl. XIV, figs. 44-48), and also 
forms in which the flagellum appears to be entirely lost 
(loc. cit., figs. 49-51). I have not found such forms in my 
preparations, but I have seen those that my colleague has 
figured. According to Koch (19) and Stuhlmann (41), such 
forms are a regular part of the life-cycle, and Robertson (37) 
also describes them in the trypanosome of Pontobdella. 
Koch describes them as arising by the break-up of large, 
multinuclear forms, possibly zygotes. Robertson, on the 
other hand, considers them to be the first form assumed by 
trypanosomes when taken up from the blood of the vertebrate. 
Both Koch and Robertson describe the formation of small 
forms from the round forms. 
As round forms are not very frequent in my preparations, 
Iam not able to make any definite statements about them, 
except that they are connected by transitions with small 
forms. Iam inclined to regard them as a normal temporary 
resting phase of the small forms, though ina few cases, 
perhaps, they may be due to imperfect fixation or other 
deformation due to technique—for instance, alterations during 
the dissection of the fly before fixation, when owing to any 
cause the making of smears has been delayed.: 
In all the different varieties of the ordinary form, as I have 
