112 
HerjMomonas and Cidthidia 
The nucleus contains a peripheral chromatic area and one or more 
central granules. During the cellular division (Diagram II, Figs. 1-8) 
the flagellate becomes shorter and broader, the blepharoplast becomes 
spindle-shaped (Figs. 2, 3) and the nucleus larger (Figs. 1-3). The 
nuclear division seems to be a promitosis, tlie karyosome becoming 
elongated (Fig. 4) and dividing (Fig. 5). After division, the two 
daughter-nuclei remain united for some time by a chromatic filament 
(Fig. 6). The formation of the new flagellum proceeds in the same 
way as I described (1910) in Trypanosoma lewisi. A short flagellum 
(flagellar root) is produced by tlie base of the old flagellum and grows 
out independently (Figs. 1-3, 5, 6). The dividing forms are 9-13 fi 
long, and 5-6 p broad. 
In never-dried preparations, fixed with corrosive alcohol and stained 
with iron-haematoxylin (Diagram I, Fig. 9), the blepharoplast does not 
show any structure, owing to the fact that the achromatic portion of 
this oi’ganellum is left uncoloured. The nucleus stains deeply, without 
any differentiation, and is surrounded by a clear halo, due to the 
contraction of the nuclear substance. Similar figures have been 
mistaken for a nucleus containing a large karyosome, and clearly 
illustrate how defective is this method of fixing and staining. 
III. Herpetomonas galliphorae Swingle. 
This species has been described recently by Swingle (1911). In 
his description H. calliphorae and Grithidia Galliphorae are thrown 
together. There can be little doubt, however, that they are distinct 
species, as the morphology and the mode of division are quite different. 
The prevalence of this parasite in the flies varies according to the 
time of the year. In August (in Amsterdam) 2470 of the flies caught 
were found infected; in October, 50 "/o were infected: in November, 
24 "/o. The few flies caught during the time from December till March 
were apparently not infected, but a few post-flagellate stages may have 
been overlooked. 
1. Flagellate stage. 
The non-dividing flagellate is 10-25 p long (without flagellum) and 
2-3 p broad ; the whole flagellum is 43-45 p long, the extracellular 
part of it 39-40/4. Sometimes very slender forms are to be found 
(Diagram III, Fig. 3) measuring 23/4 iu length and only l’2/4 in 
