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Herpetomonas jaculum (Leger) 
Sexuality in Herpetomonas jaculum. 
Much has been written from time to time of sexual dimorphism in 
the Trypanosomatidae. I do not propose to enter into the subject very 
fully here, except in so far as it relates to Herpetomonas. Up to the 
present Prowazek appears to be the only writer who has attributed 
sexual characters to Herpetomonas. According to Prowazek H. muscae 
domesticae has three forms of individuals, male, female and indifferent, 
size and granulation being the criteria for their separation. Apparently 
the involved processes described by Prowazek as occurring before, during 
and after copulation, were only studied by him in stained preparations. 
Copulation has apparently never been observed in vivo in the Trypano¬ 
somatidae. 
Size as a criterion of sex does not hold, for the following reasons: 
(a) Herpetomonas jaculum obtained from large, adult Nepa are 
frequently larger than those from the nymphs. 
(b) H. jaculum in the rectum divides very rapidly, and I have 
watched one individual divide and produce two daughter forms, each of 
which again divided. But these very small forms were not male forms, 
for they lost their flagella and became encysted—but if thinness and 
small size were to be considered, emphatically they should have been 
male forms and should have behaved accordingly. 
(c) Regarding the presence of much granular protoplasm as being 
characteristic of female forms and its absence being the usual condition 
in males, I would cite the following experiments: 
On one day I collected a number of active, healthy Nepa, and 
dissected half of them, the others being put into an aquarium. All 
of those dissected had recently fed on blood, either of a fish or of an 
amphibian, unchanged nucleated red corpuscles being present in the 
blood contained in the crops of the Nepa. All were infected with 
H. jaculum , and in every case the body of the parasite contained very 
many large, refractile granules, apparently of reserve food material. 
The bodies of the organisms also were broad. My preparations, if the 
sex criteria quoted above be called into consideration, contained female 
Herpetomonads. Three days later, I dissected the remaining Nepa, 
that had not been fed during that period. They, too, were infected with 
H. jaculum, but the Herpetomonads w T ere long, slender forms, whose 
bodies showed few or no granules in them: in other words, they were 
“male” forms. I interpreted the occurrence of few granules in these 
