A. Porter 
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pass along the body-myonemes (PI. V, Figs. 20, 21) from the posterior 
end towards the flagellum. The appearance of the organism is entirely 
altered thereby, the waves causing the flagellar end to swell out and 
become ball-like, so that the organism more or less resembles a peg-top. 
Relaxation follows this contraction, and the flagellar end seems to 
spring forwards with a jerk, this really being due to the release of the 
tension of the ectoplasm of the rounded part of the organism. The 
rolling movements continue concurrently with those of contraction. 
As I have seen this movement occur while the Herpetomonas was 
within the unruptured gut of the Nepa, I do not think it can be 
regarded as an abnormal one. 
Reversal of the direction of movement frequently occurs. It is 
accomplished very rapidly. The flagellum swings out suddenly in a 
semi-circular direction, and so great is the impetus of movement, that 
the body is swung round by the flagellum, and the two come to lie in a 
straight line with one another. The spirally boring and lashing move¬ 
ments of the flagellum, usually accompanied by those of contraction 
and relaxation of the body, are re-commenced, and the organism moves 
away in the direction opposite to that in which it was progressing 
before. 
Sometimes a parasite is seen whose flagellum hardly moves at all 
and yet it progresses forwards with ease. A gentle, undulating move¬ 
ment of the body from side to side is all that is obvious, the movements 
of the flagellum being so slight as to be hardly noticeable. 
Many peculiar movements, due to the flagella of two parasites 
becoming entangled, have been seen. Organisms entangled thus have 
rotated for many minutes with great speed, the point of entanglement 
acting as a centre about which the rotation occurred. These forms 
have invariably separated from one another finally and swam away. 
Morphology. 
There is much variation in the gross morphology of Herpetomonas 
jaculum as seen in different parts of the gut of the host. Small rounded 
or oval pre-flagellates and later pre-flagellates are most abundant in the 
crop; fully flagellated organisms are specially abundant in the stomach 
and early part of the intestine, while in the rectal portion of the 
intestine there are numerous short forms, which are in process of 
division and also of eucystment. These post-flagellates also occur in the 
faeces. 
