74 FRANK R. LILLIE. 



these statements, but there would not be much value in multiply- 

 ing instances by describing all of the intermediate conditions. 



The same configuration is found in all stages of maturation 

 and fertilization up to the first .cleavage, at which time the cleav- 

 age naturally causes modification. Whether or not it reappears 

 in each cell is a question that I have not examined. 



It maybe objected that the configuration shown could be pro- 

 duced as readily by mass movements of the protoplasmic areas 

 as by individual granule movements. But such a conception would 

 meet a fatal difficulty in the case of the central spongy area ; the 

 basophile cap in the central end (with reference to the centrifuge) 

 of this area could not be produced in any other way than by 

 a granule movement. Moreover, detailed examination of the 

 movements in the spherular zone (Fig. 4, j) seem to me to be 

 equally conclusive : If the movements produced by centrifugal 

 force in this area were mass movements of the protoplasm as a 

 whole the conformation of this zone should vary with the direc- 

 tion of the centrifugal force until it reached a final position of 

 equilibrium, for the reason that it would fold in different ways 

 around the central spongy area. The graded series of centri- 

 fugal forces employed may be regarded as showing stages in the 

 segregation of the granules of this area. If the movements were 

 mass movements the animal pole extensions of the spherular zone 

 (Fig. 4) must wrap around the central spongy area where the 

 centrifugal force acts at any appreciable angle from the egg-axis. 

 But this is not the case ; the proximal pole of the spongy area 

 is never covered by such a fold. With the lowest speed, in 

 directions at any appreciable angle to the egg-axis, one finds 

 that the hyaline zone is dotted with granules of the spherular zone, 

 evidently caught in migration ; such granules are rarer with suc- 

 cessively higher powers of the centrifuge, until they are practi- 

 cally absent. It is obvious that they pass individually across the 

 hyaline zone. 



Another conclusive proof of individual granule movements is 

 shown in Fig. 9. The spindle is in a very high degree resistant 

 to penetration, and it therefore often acts as a block to migrating 

 granules, which pile up against it. The figure illustrates the 

 blocking of fat granules which are for the most part accumu- 



