262 Herpetomonads 
these bodies are of the nature of reserve food-stuff or of excreta. I was 
unable to detect the posterior diplosome of Prowazek. 
The above is a description of the adult flagellate from the fly: it is 
well to compare with it the corresponding stage from the larva (fig. 26). 
Here individuals are smaller, the rhizoplast is much shorter, the kineto- 
nucleus is smaller, '8/j,, stains more evenly, and tends to be circular, the 
tropho-nucleus is placed further forward in the body, the granules in 
the cytoplasm are few in number, and restricted to the extreme posterior 
end. 
The interesting experiments of Miss Porter (1909) leave no doubt 
that these granules in the cytoplasm of herpetomonads are an expression 
of the degree of metabolic activity, and must not be taken as an 
indication of sex. This author states that H. jaculum in a highly 
nutritive medium developed large numbers of refractive granules, and 
when deprived of food, proportionately few. In the case of the flagellates 
at present under discussion, the smaller size and clearer cytoplasm of 
the parasites from the larval gut may well be explained by their 
much denser crowding there and the relatively small food supply per 
individual. 
Division is longitudinal. The rhizoplast usually divides first, and it 
can be seen that each half carries with it a basal granule (figs. 12 and 
23). I have never found stages in which the new rhizoplast was growing 
up from the basal granule. I am therefore inclined to believe that to 
this extent there is splitting of the flagellum root. Beyond this point, 
however, I consider that the second flagellum is a new formation, and 
does not arise by splitting of the original flagellum 1 . Figs. 12 to 17 
illustrate this very well. For some time the two flagella lie closely 
together, and this may last until the new flagellum has almost reached 
the length of the first, producing the deceptive appearance of a bi- 
flagellate organism. This is most frequently the case in the parasite in 
the fly. In the larva, for some obscure reason, the splitting of the 
flagellate body usually takes place at an earlier stage in the formation 
1 There is great diversity of opinion as to the mode of origin of the new flagellum in 
H. muscae-domesticae and allied forms. Prowazek (1904) describes the new flagellum in 
H. muscae-domesticae as growing up from the divided basal granule, which he figures at 
the point of emergence of the flagellum: from this later on in like manner a new rhizoplast 
grows down. Patton (1909), referring to the same flagellate, finds that longitudinal fission 
begins with a splitting of the flagellum root. Miss Porter (1909) states that as in H. 
jaculum she has “watched the flagellum of the living II. muscae-domesticae divide in two.” 
My own observations on this parasite are in agreement with those of Berliner (1909) on 
II. jaculum. 
