380 
Herpetomonas jaculum (Leger) 
make such assertions. Preceding cyst formation, there are two successive 
divisions of H. jaculum, whereby small daughter parasites are produced. 
This decrease in the size of the parasite is opposed to the idea of 
autogamy. I have never seen any form either of autogamy or of sexual 
dimorphism in H. jaculum, H. muscae domesticae, H. culicis or H. vespae, 
n.sp. 1 , all of which I have observed in the living condition. Nor am I 
alone in this. Neither Leger nor Patton have seen clearly defined 
sexuality in the Herpetomonads that they have investigated. 
Mode of Infection. 
The mode of infection of Nepa cinerea by H. jaculum may be casual 
or hereditary or both. Regarding the first method, careful atteution 
has been given to the habits of Nepa cinerea, both in their natural 
breeding grounds—a matter of some difficulty—and also in captivity in 
an aquarium. 
The Nepa are found to breed among leaves of aquatic plants, the 
chief being Lemna major, Elodea canadensis, Potamogeton crispus (in 
one locality), Veronica beccabunga and Hydrocharis morsus ranae. 
Their faeces are voided on the leaves of these plants, forming blackish 
patches and having a peculiar odour in mass. Examination of the faeces 
showed flagellate Herpetomonads and cysts. Young Nepa move about 
among these leaves and suck up the faeces with the moisture. Indi¬ 
vidual Nepa so engaged have been watched carefully, seized quickly 
and the mouth region of the bug pressed against a clean slide. The 
small amount of darkish material so obtained, when stained and 
examined microscopically is found to contain cysts. Immediate 
dissection of the crop of the same Nepa also has shown that cysts are 
present in its contents, while in the case of very young nymphs, no 
parasites were present in the rest of the crop, so that the ingested cysts 
would cause a primary infection of the nymph. 
This certainly is definite evidence of casual infection, agreeing 
therein with what Patton (1908-9) has described for H. lygaei and 
H. muscae domesticae where the same method of infection prevails. 
Berliner (1909) has noted this method of infection also in connection 
with H. jaculum but does not give experimental proof of his statement 
1 I wish to record the occurrence of a new Herpetomonad, parasitic in the alimentary 
tract of the hornet, Vespa crabro. I have named this flagellate Herpetomonas vespae, and 
hope to publish an account of it shortly. 
