C. M. Wen yon 
351 
group, consists of a dark-staining granule, the parabasal, in front of which is 
a paler and smaller granule, the blepharoplast or centrosome from which the 
rhizoplast, continued into the flagellum, actually arises. Between these two 
granules, and also frequently behind them, is a clear area. Whether the whole 
structure represents a true nucleus of which the dark granule is the karyosome 
and the limits of the clear area a nuclear membrane on which the centrosome 
lies, as in the nucleus of Cercomonas, is still a matter requiring elucidation. 
I have brought forward some evidence in favour of the true nuclear nature of 
this structure in a paper entitled “ Observations on Herpetomonas muscae do- 
mesticae and some Allied Flagellates 55 (1913). Most observers, however, seem 
to regard the structure as not being a nucleus and I quite agree there are many 
arguments against this view. Kofoid (1915) has suggested the abandonment 
of the name kinetonucleus and with it the binucleate conception of this group 
of flagellates. According to him the darkly staining granule is a parabasal 
body, a term first used by Janicki (1911), and homologous with similar struc¬ 
tures which are associated with the flagellar origin in many other flagellates 
(Trichomonas, Chilomaslix, Giardia, etc.) and which occurs in the flagellate 
Prowazekella lacertae considered below. The blepharoplast is the centrosome 
and leads the way in division. It must be admitted, however, that in division 
the behaviour of the centrosome and the subsequent division of the darkly 
staining mass by elongation and constriction, evidently under the influence 
of the centrosome, bears a striking resemblance to the division of the tropho- 
nucleus of these flagellates or of the nucleus of Cercomonas, as I have shown 
elsewhere (1913). Whether there is a nuclear membrane or not surrounding 
the clear area in which the darkly staining granule lies is largely a matter of 
interpretation, for one is dealing with such tiny objects that it is exceedingly 
difficult to determine this point with accuracy. In such a decision one is 
naturally influenced by what one has observed in larger flagellates. On account 
of the doubt surrounding the true nature of this structure it is better to avoid 
any term implying a nuclear nature so I have adopted the name kinetoplast, 
first suggested, I believe, by Alexeieff. The use of this word avoids the neces¬ 
sity of such ponderous names as kinetonucleus and trophonucleus. The kineto¬ 
plast includes both the parabasal and the blepharoplast. In degenerate try¬ 
panosomes in which the cytoplasm has disappeared the kinetoplast may re¬ 
main as a compact body showing the parabasal surrounded by what appears 
to be a membrane on which the blepharoplast lies. The flagellum may or may 
not remain still attached to the blepharoplast. 
As a rule the cytoplasm of the organisms is quite clear. In some, however, 
darkly staining granules are present, but these are probably dependent upon 
the state of nutrition. 
The length of the body of the largest individuals (PI. XX, Fig. 1,/and m) is 
about 15 /jl and the flagellum is slightly longer than this. The width of the body 
of these long forms is under 3 /z. From these there may be traced a series of 
gradually diminishing individuals of a great variety of shape and size, as shown 
