THE HJIMOFLAGELLATES. 229 



some way pass out into the cytoplasm, leaving, finally, only the faintly or 

 non-staining plastinoid basis (fig. 21 a) ; or else direct fragmentation of the 

 nucleus occurs (f — j), this being probably a modification of the former 

 method. At other times it is apparently the kinetonucleus which undei*- 

 goes fragmentation. This is so in T. lewisi, according to Prowazek, and 

 from some of his figures of the parasites the process would certainly seem 

 to bear the interpretation of abnormality. In any case, the result is much 

 the same. Chromatic lumps and grains, varying greatly as regards size 

 and number, become more or less generally disseminated throughout the 

 cytoplasm. Ligniores (1. c.) considers that this process is simply an 

 abnormal development of what is a common occurrence in many Trypano- 

 somes. It has been pointed out that in several forms chromatoid grains 

 are frequently to be noticed in the cytoplasm. This author has followed 

 the formation of such in T. equinum, and has seen them given off at 

 intervals from the nucleus.' Moreover, it has been observed that these 

 chromatoid grains increase considerably beyond their normal number in 

 individuals placed in unfavourable surroundings, and in some cases the 

 involution process, at any rate in this direction, appears to stop here. 



(b). Vacuolisation may also be regarded as a normal function carried 

 to excess. The frequent presence of a vacuole in many Trypanosomes has 

 been mentioned above, and reasons adduced for considering that this 

 structure represents a normal, though not necessarily constant, cell- 

 organella. The first indication of abnormality in this direction is perhaps 

 afforded when the vacuole increases very greatly in size, as in figs. 21 E, 

 22 E, This may be followed by the appearance of others in the cytoplasm 

 (figs. 21 c and 22 g) when the involution becomes pronounced in character. 



(c). Change of form. This is the most obvious, and at the same time 

 the most far-reaching in the effects produced, of the chief lines of involu- 

 tion. Alteration in shape is presaged and accompanied by an increasing 

 loss of mobility until the parasites can no longer move. The manifold 

 varieties which abnormal Trypanosomes may exhibit in respect of shape 

 can be most easily understood, when arranged according to the normal 

 condition or phase which they represent, and of which they are the 

 degenerative results, (i). Single forms. Examples of these are seen in 

 fig. 21. The body becomes fat and stumpy (b — e), and may entirely lose 

 its trypaniform shape, becoming ovoid or spherical — in fact, like a ball 

 (c, l). The flagellum is limp and inactive, and is often partially coiled 

 around the body (j). The undulating membrane can no longer be made 

 out. (ii). Division forms. Certain individuals may have commenced 

 longitudinal division when the change of shape just described sets in, 

 and the process is not completed. Thus result more or less rounded 



' Probably some process of nuclear excretion or readjustment is con- 

 cerned. 



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