MORPHOLOGY OF THE TRYPANOSOMES 653 



closely resemble trypanosomes in structure). This microniicleus 

 is often surrounded by an unstained halo, and in its neighbour- 

 hood, in certain species, a vacuole has been described as existing. 

 From the micronucleus or from its neighbourhood there arises an 

 important structure in the trypanosome, — the nndulatory mem- 

 brane. This is of varying breadth, has a sharp undulating free 

 margin, and surmounts the protoplasm of the organism like a 

 cock's comb ; it narrows towards the anterior end, where it be- 

 comes the flagellum. Motion is chiefly effected by the undulations 

 of this membrane and of the flagellum. The latter is continuous 

 with the protoplasm of the body of the organism ; it stains 

 uniformly like it, except the free edge which has the reddish 

 hue of the chromatin. In different species of trypanosomes, 

 variations occur in shape, in length, in breadth, in the position 

 of the micronucleus (and therefore in the length of the undulat- 

 ing membrane), in the breadth of the membrane, in the length of 

 the free part of the flagellum, in the shape of the posterior end, 

 which is sometimes blunt, sometimes sharp, and in the presence 

 or absence of free chromatin granules in the protoplasm. It 

 may be said that the differentiation of species of trypanosomes 

 is often a task of great difficulty, as both morphological and 

 experimental study is necessary. l 



Multiplication in the body fluids ordinarily occurs by 

 longitudinal, amitotic division. First of all, the micronucleus 

 divides, sometimes transversely, sometimes longitudinally, then 

 the macronucleus and undulating membrane, and lastly the 

 protoplasm. In some species the root of the flagellum only 

 divides, so that in the young trypanosomes the flagellum is short 

 and subsequently increases in length (Tr. lewisi) ; usually the 

 whole flagellum takes part in the general splitting of the 

 organism. In certain cases reproduction occurs by the endo- 

 genous formation in the nucleus of chromidial buds (Minchin). 

 These buds are the " infective granules " of Henry and other 

 observers, and when extruded from the protoplasm develop into 

 trypanosomes. 



In most cases in the circulating blood the parasites of a 

 species show differences in shape and size; usually there is a 

 form long and slender in both body and nucleus, the free part 

 of the flagellum being longer than the body and the protoplasm 

 free from granules. In another type the organism is broader, 

 with a larger and rounder nucleus and a blunter posterior 

 extremity; the undulating membrane is narrow and the free 

 part of the flagellum is shorter than the body, and the proto- 

 plasm contains granules. According to one view, the former is 



