HEUrETOMONAS LYGJil 181 



and shows a slight coustrictiou iu its middle, producing a dumb-bell like appearance. 



Division of the kinetonucleus then occurs, followed by division of the trophonucleus, 



and longitudinal division of the cell wall and its cytoplasm, and two separate parasites, 



each containing a tropho- and a kinetonucleus, are thus formed. The anterior ends 



of the parasite are usually directed towards one another or lie in close apposition. Each 



parasite may again go through the same process of division, and four or more parasites 



be thus formed. The further stage of development continues in the crop. Most of these 



parasites pass into the stage of flagellation while others may yet divide again before 



becoming flagellates. In those parasites that undergo further development, the anterior 



end becomes elongated and the kinetonucleus moves farther from the trophonucleus. 



This is followed by elongation of the posterior end of the parasite and the development of a Further stages 



vacuole anterior to the kinetonucleus ; from this vacuole a pale pink filament can be seen 



developing. This represents the flagellum (Plate XI., figs. 7-9). Longitudinal division 



may then occur, the line of cleavage usually commencing at the anterior end of the 



parasite. Many of the parasites at this stage show marked vacuolation, especially at 



their posterior extremity, and appear as short stumpy tadpole forms with thickened 



kinetonuclei and flagella. The trophonucleus is often stretched out with its long axis 



running transverse to the parasite. All these various stages of development up to mature 



flagellates may be seen in the crop ; the mid-intestine, however, shows the largest number 



of typical adult flagellates. These adult flagellates measure on an average 26/j in length 



and 2/^1 in breadth. In api^earance they are somewhat cigar-shaped, with sharp pointed 



posterior ends, and blunt rounded anterior ends from which the flagella extrude. The 



cytoplasm is vesicular in structure, and often contains pink-coloured granules, especially 



in the posterior portion of the parasite (Plate XI., figs. 10-14). 



If an iron hematoxylin stain be employed it is quite apparent that these granules 

 are not of a chromatin nature, for the cytoplasm is stained very uniformly in this area, 

 showing, perhaps, a slight reticular structure, but rarely anything that could be considered 

 chromatic granules. It is difficult to say what these granules represent ; in all probability 

 they are of the nature of reserve foodstuff. Porter' is inclined to think they represent 

 metabolic changes as they are usually present when the parasite is in a highly nutritive 

 medium, but, when deprived of this medium, the granules present are but few iu number. 

 This view is supported by the fact that herpetomonads present in the gut of bugs that have 

 been starved for a few days show practically no granules in their cytoplasm, while those 

 herpetomonads removed from bugs that have been recently feeding have a marked granular 

 cytoplasm. The trophonucleus is, as a rule, circular in shape and occupies more or less a 

 central position in the parasite. Around its margin is a definite nuclear membrane 

 containing chromosomes ; these are more apparent in specimens stained by Giemsa than by 

 Leishman's stain. In iron hsematoxylin specimens the nuclear membrane is well brought .^ nuclear 

 out but no central karyosome is evident. membrane 



The kinetonucleus occupies a position anterior to the trophonucleus, and is usuallv 

 4/1 distant from it. In adult flagellates it is invariably rod-shaped, running transverse 

 to the long axis of the parasite, and is placed about 4/i from the anterior extremity. The 

 cytoplasm between the tropho- and kinetonuclei stains quite uniformly and shows no 

 evidence of the spiral " Doppelfaden " described by Prowazek in H. miiscas domestic^. 



Immediately in front of the kinetonucleus is a small achromatic space, on the anterior 

 margin of which there appears a slight thickening of the cell cytoplasm in the form 

 of a small rod or dot. This is rarely seen except in films fixed by a wet method. 



' Porter, A. (1909), " The life cyele of Herpdomonas jaculuiu" Leger. Parasitology , Vol. II., pp. 367-391. 



