IO4 FRANK R. LfrLLIE. 



tutes a cap of granules of intermediate size that give a fatty reac- 

 tion with osmic acid and are soluble in oils. The intermediate 

 stratum, forming a hyaline band, contains very minute granules 

 that take the basic stain ; they may therefore be called basophile 

 granules. The distal stratum occupies the distal hemisphere of 

 the egg and is composed of larger granules of yellow tinge, usu- 

 ally called yolk granules, which take the acid stain and may be 

 known collectively as acidophile granules. The chromatin and 

 the spindle have the same specific gravity as the basophile gran- 

 ules, as is proved by the fact that they are found in the hyaline 

 band when they move freely. 



The movements of the granules, and consequently their segre- 

 gation, are modified by differences of resistance within the ground 

 substance. The latter has four concentric zones (Fig. 3, A), (i) 

 a central more fluid area (Fig. 3, A, 2), (2) a dense zone bound- 

 ing the latter (Fig. 3, A, 3), (3) a second more fluid zone specially 

 developed in the region of the spindle (Fig. 3, A, 4), and (4) an 

 ectoplasmic zone defective at the outer end of the spindles (Fig. 

 3, A, 5) (see Lillie '09). 



All zones contain both basophile and acidophile granules (Fig. 

 i). Under the action of centrifugal force, therefore, the granules 

 move relatively freely through the more fluid zones and are im- 

 peded in their movements in the denser zones. The consequence 

 is that when low centrifugal speeds of short duration are used, 

 there is a tendency for the granules to aggregate in the dense 

 zones. Thus the basophile granules of the central more fluid 

 area aggregate in the central end of the dense zone bounding it 

 (Fig. 2) and the acidophile granules in the distal end. The 

 basophile granules of the outer fluid zone aggregate proximally 

 with reference to the axis of the centrifuge and the acidophile 

 granules aggregate distally, and therefore lie external to the inner 

 dense zone and within its walls, but do not pass through the 

 latter to enter the central more fluid area (Fig. 2). The most 

 important of these aggregations with reference to the interpreta- 

 tion of the karyokinetic figure is the basophile cap found in the 

 central end of the inner dense zone (Fig. 2, b.c]. 



The distortion of the ground substance is of the following 

 character: (i) the egg is invariably somewhat elongated in the 



