A. Porter 
369 
with vaseline. The parasites could then be watched for a considerable 
time. In ver} 7 young specimens of Nepa the gut was extremely trans¬ 
parent, and the parasites could be seen moving about within it. 
For purposes of comparison several stains were used. Giemsa’s 
stain was of great service in giving a general idea of the morphology of 
the parasite, though the tendency of this stain to exaggerate the 
chromatin needs to be checked by the use of others. Iron-haematoxylin 
followed by orange-G, thionin, and Delafield’s haematoxylin, either 
alone or followed by orange-G, were all found of much service. Twort’s 
stain (neutral-red and Lichtgriin) and safranin were also tried. 
Intra-vitam staining was not of much assistance, but methylene- 
blue proved superior to neutral-red. 
General Description. 
Herpetomonas jaculum has three phases in its life-history. Taking 
as the first, the pre-flagellate stage, the parasite exists as a small, oval, 
cyst-like body (PI. V, Figs. 1—6), possessing two chromatin masses, that 
is a true nucleus and a blepharoplast. The flagellum arises near the 
blepharoplast, elongates and grows out, till the organism gradually 
reaches the second phase of its life-history, that of the fully formed 
flagellate. 
The flagellate form (PI. V, Figs. 19—36) is the most commonly 
occurring one. The body of the flagellate parasite is from 13 ji to 33 /r 
long and from 1 /jl to 4 p broad. The free flagellum is about as long 
again as the body. The body is elongate and is rather blunt at its 
flagellar end, not so tapering as is the case in Crithidia. The long, 
gregariniform, oval body shows clear ectoplasm and a granular endo¬ 
plasm, though granules are far less numerous than in Critliidia, nor is 
the endoplasm so alveolar in nature. Each parasite possesses an oval 
nucleus, usually nearer the flagellar end of the body, and a rod-shaped 
blepharoplast is present, near to which the flagellum arises. A single 
flagellum is present, but in many adult flagellates there is an appearance 
of two flagella near the body end (Figs. 38, 39), as the flagellum 
divides precociously, even before the organism has completed its growth, 
and before the body as a whole divides longitudinally. The process 
of division takes place repeatedly during the flagellate stage of 
existence. After a number of successive longitudinal divisions, some 
of the forms resulting therefrom (Figs. 51, 52) reach the rectum. 
Here again division longitudinally occurs and the result is the pro- 
