372 Herpetomonas jaculum (Leger) 
Flagellates occurring in male Nepa cinerea are often much more 
slender than those obtained from females. Parasites occur in the 
ovaries and are very broad. They have not been found in the testes of 
Nepa. The significance of the forms in the ovaries will be discussed 
later. 
The Pre-flagellate Stage. 
The pre-flagellate stage of H. jaculum is best observed in the crop of 
the young nymphs of Nepa cinerea. Here may be found, together with 
some fully formed flagellates, all forms leading up to the adult flagellate. 
Commencing as small cysts (PL V, Fig. 1), probably ingested with the 
faeces of another Nepa, the adult flagellate is gradually developed. 
The oval pre-flagellates (Figs. 1—6) measure from \g to og long, and 
from 2g to 2'bg broad. 
Each young form becomes somewhat oval. Internally it consists of 
a nucleus, usually oval (PI. V, Figs. 1, 2) or round (Fig. 12), and lying 
often to one side of this is a more or less rod-shaped blepharoplast 
(Figs. 1, 4, 15), surrounded by the cytoplasm. In this respect H. jaculum 
is very like H. lygaei as described by Patton (1908). An area (Figs. 2, 4) 
staining much like chromatin and somewhat variable in position is 
often present. As growth proceeds, a thread, staining pink with Giemsa 
and purple with Delafield, makes its appearance at the side of the 
organism (Figs. 5, 6), having originated from the area before mentioned, 
and near to the blepharoplast. This thread grows out as a kind of 
small tag at first near the body (Figs. 7—10), later extending beyond 
it (Figs. 11—14) and sometimes gradually drawing out the body after 
it for a very short distance only (Figs. 15, 16). The end of the body 
opposite to the flagellum also elongates (Fig. 17), the body becomes 
spindle-shaped and the appearance of the adult flagellate then is 
assumed. 
The Flagellate Stage. 
The following points regarding this, the best known stage of 
Herpetomonas jaculum, are in addition to those given in the general 
description. 
The ectoplasm is clear and flexible. Myonemes (PL V, Figs. 20, 
21, 38) are present in it and can be seen on staining somewhat deeply. 
The contractile movements of the body are in part due to these 
organellae. 
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