ABSTRACT AND REVIEW. 103 



nor chromatin granules, for the small peripheral granules (see 

 below) go blue when stained with iodine-green fuchsin, or 

 methylene-blue acid fuchsin^ while the central granules colour 

 red. Next there is a zone free from granules, and traversed only 

 by achromatic threads, between which is the so-called nuclear 

 fluid ; this zone varies in breadth, but may occupy as much as 

 one fifth of the whole diameter. Around this clear zone, again, 

 is the outermost of all, which may be in breadth as much as two 

 thirds of the whole diameter, but which varies with the width 

 of the clear zone. It contains numerous small deeply staining 

 granules of chromatin, occasionally equalling the nucleoli in 

 size. The division of the nuclei is apparently amitotic. 



b. The Chroraatophores. — No ''diffuse chlorophyll" can 

 be detected either in the amcebse or in the cysts. The pigment, 

 yellowish or brownish green, is always contained in definite 

 though very minute corpuscles. These are either discoid or 

 lens-shaped, appearing fusiform in profile, or may be nearly 

 spherical, sometimes angular or lobed. In the largest chroma- 

 tophores the thickness varies from \\ n to 2/x, the diameter 

 from 4^ju to 5^,u, but the size seems to vary inversely with the 

 number. In the amoebae, as also in the mature and in the 

 uninuclear cysts, they are generally very small indeed, about 

 ^ ju in diameter, which may account for the diffuse chlorophyll 

 of other authors. They attain their maximum size in the adult 

 but still immature cysts. 



In the uninjured cell very little structure can be detected 

 in the chromatophores, except now and then darker spots on 

 a lighter ground substance, due, perhaps, to thicker accumu- 

 lation of the oil which lies in the chromatophoric reticulum 

 (Fig. D, 7, 8). But when fixed, and with the oil and pigment 

 removed by alcohol, a skein-like structure of threads twisted 

 over one another exhibits itself. These threads are composed 

 of rounded segments, Mayer's granules, and can be readily 

 stained. In the smaller chromatophores there is only one 

 twisted thread, but in the larger several. This fibrillar struc- 

 ture can be readily seen and the threads isolated by crushing 

 the chromatophores under the cover-glass, or by prolonged 



