212 THE HAEMOFLAGELLATES 



Minute Strudwre. The body appears to lack any distinct 

 limiting membrane or cuticle. A differentiation of the peripheral 

 cytoplasm in the form, of an ectoplasmic layer, the so-called " peri- 

 plast," has only been definitely described in a few cases (Prowazek 

 [68], Wasielewsky and Senn [86]). Nevertheless, it is probable 

 that in most Trypanosomes there is such a layer, although it may 

 be, in some forms, only poorly developed around the body generally. 

 The undulating membrane, however, is certainly largely, if not 

 entirely an ectoplasmic development. This is usually much clearer 

 and more hyaline in appearance than the general cytoplasm. The 

 latter is finely granular or alveolar in character, though its exact 

 degree of coarseness and density varies in different forms, some- 

 times even in different parts of the same individual. The cyto- 

 plasm of male forms is in general clearer and less granular than 

 that of female ones. The cytoplasm in T. mega and T. karyozeukton 

 is rather unusual in structure. In the third of the body on the 

 aflagellar side of the nucleus, it is very loose and spongy ; in the 

 other two -thirds, it is arranged in alternating light and dark, 

 densely-staining bands ("hyaloplasm" and " spongioplasm "), run- 

 ning more or less longitudinally. 



Cytoplasmic inclusions of one kind or another are often to be 

 found. In many Trypanosomes, deeply -staining granules occur, 

 which vary greatly in number and size. These granules appear 

 to be chiefly distributed, as a rule, in the flagellate half of the 

 body (Fig. 7, B, D). They are of a chromatoid nature, and probably 

 derived from the nucleus (see Lignieres [54]). In Trypanophis there 

 are one or two rows of highly refractive, yellowish inclusions run- 

 ning the length of the body (Fig. 30). It is thought that these 

 represent collections of fatty or oily substances. In certain forms, 

 a well-defined, usually oval vacuole is often, though not constantly 

 present, situated at a varying distance from the aflagellar end (Figs. 

 7, c, G ; 8, F). There is no reason to doubt that this vacuole is a 

 normal cell-constituent, for it has been observed in parasites in their 

 natural (tolerant) hosts under quite normal conditions. 



Until recently, very little was known with regard to the 

 details of nuclear structure. A Trypanosome was merely described 

 as possessing an unmistakable nucleus, and also a small deeply- 

 staining element of uncertain significance, situated at the root of 

 the flagellum, and termed variously " blepharoplast," centrosome, 

 or micronucleus. It is to Schaudinn that we are indebted for the 

 revelation of the essential nuclear nature of the latter organella, 

 its intimate connection w.ith the larger nucleus and the complexity 

 and differentiation which the whole nuclear apparatus may 

 exhibit. Since then several workers have brought forward 

 observations relating to one point or another, which, taken alto- 

 gether, suggest strongly that the nuclear organisation of Trypano- 



