72 FRANK R. LILLIE. 



form of aggregation of the acidophile granules, which tend on 

 this account to pass around and not into it. It also explains the 

 more striking character of the spongy area in the centrifuged and 

 the control eggs (cf. Figs. 6 and 4), because the granules within 

 this area are free to segregate at its ends, but those without are 

 prevented from entering. 



Similarly, the persistence of the granules in the ectoplasmic 

 zone indicates that this is another region of greater density of the 

 ground substance. It requires a much greater centrifugal force 

 to dislodge these granules than those lying within the egg, but 

 when they are so dislodged they appear to be the heaviest class of 

 granules within the egg, for they aggregrate at the distal pole 



(Fig- 9)- 



The following diagrams (Fig. 8) illustrate both the conception 



of the ground substance to which I have come as a result of the 

 experiments, and the effect of the centrifugal force on the ground 

 substance itself: The latter consists of four concentric layers, 2, 

 3, 4 and 5 (Figs. A and C] ; of which 5, the ectoplasmic stratum, 

 is relatively dense, 4, the zone containing most of the acidophile 

 granules of the normal egg is relatively fluid, 3, again, is a dense 

 ring-shaped zone, surrounding 2, the central, more fluid spongy 

 area. 



The egg is an elastic sphere ; it therefore undergoes elonga- 

 tion in the direction of the centrifugal force (Fig. 8, B and D ) ; 

 this is perfectly obvious immediately after centrifuging. The 

 arrows in the figures to the left indicate the direction of the cen- 

 trifugal force and the figure to the right in each case represents 

 the result. Now observation shows that the spongy area of cen- 

 trifuged eggs lies in the distal hemisphere, hence elongation of 

 the ground substance must have taken place on the central side, 

 owing presumably to the tension of the specifically very light 

 substances (e.g., fat globules) found here. 



I have employed five or six different degrees of centrifugal 

 force in examining this question and have made a considerable 

 number of experiments with each. The configuration which we 

 have just described varies somewhat with different degrees. With 

 less force the same configuration is found down to 575 revolu- 

 tions in 17 seconds with a radius of 13 cm. With higher forces 



