374 
Herpetomonas jaculum (Leger) 
I have never been able to find any evidence of complicated reducing 
divisions such as Prowazek (1904) described in the case of Herpetomonas 
muscae domesticae. 
Chromidia are found in H. jaculum and are usually widely 
separated one from another (PI. V, Figs. 28, 33, 34). They are not so 
abundant as in H. lygaei. Chromidia occurring either singly or in small 
groups near the posterior end of the body of H. jaculum probably 
explain the “ posterior diplosomes ” of some authors (Figs. 28, 
32—34, 37). 
The Flagellum is very noticeable in H. jaculum. It develops in the 
late pre-flagellate stage of the parasite from a chromatin-like staining 
area near the blepharoplast. The flagellum emerges from the body as 
a single element (PI. Y, Figs. 11—16), and remains single for a short 
time, whilst the body of the Herpetomonas elongates (Figs. 15, 16, 17) 
and gradually assumes the typical, gregariniform appearance (Figs. 
19—36). The flagellum is much thicker at its origin than it is distally. 
A basal granule (blepharoplast of Minchin) (Figs. 8, 12, 22, 34, 35) is 
very near the oi’igin of the flagellum, at times touching it, and lies 
between the root of the flagellum and the blepharoplast. 
The organism at this stage is ready for active multiplication by 
division, and slight constriction of the blepharoplast appears, accom¬ 
panied by a separation of the lower part of the flagellum into two 
portions (PI. V, Figs. 37, 38). The condition of the organism at this 
time resembles that figured by Prowazek (1904) for H. muscae domesticae. 
Now, it frequently happens that practically every Herpetomonas jacidum 
in one Nepa is in this condition at the same time, and as a lull in the 
process of division occurs here, it would be very easy to mistake this 
condition for that normally present in the parasite, and to state, as 
Prowazek has done for H. muscae domesticae, that two flagella united 
by a membrane are present. 
Having recently examined Musca domestica for the purpose of 
comparing H. muscae domesticae directly with H. jaculum, I found that 
in many flies, every Herpetomonas in each fly showed but a single 
flagellum; also that the flagellum commenced to divide before the rest of 
the organism, but that the split never extended very far—in fact, that 
the division was delayed for some time after its initiation. In other 
flies, practically every H. muscae domesticae seen exhibited the so-called 
“double flagellum,” and in the former cases, the phenomenon is only 
that of precocious division of the flagellum. The matter can only be 
finally decided in H. muscae domesticae by carefully tracing out the 
