KARYOKINETIC FIGURES OF CENTR1FUGED EGGS. IOQ 



the aster. If the spindle moves in the direction of its own axis, for 

 instance, the rays of the forward aster must tend to be bent back 

 about the spindle, and those of the other aster away from the 

 axis. Similarly, there should be definite configurations charac- 

 teristic of every angle and amplitude of movement. But, if the 

 rays are expressions of forces centered at the poles and are there- 

 fore composed of oriented particles (centrosome hypothesis), such 

 disarrangement of the radii would not be expected to result from 

 movements of the spindle, except to the extent involved in the 

 inertia of the substances concerned. 



In a considerable number of experiments it was my aim to 

 kill the eggs in the shortest possible time after centrifuging. 

 The tube was removed from the centrifuge as quickly as pos- 

 sible, the water poured off and the killing fluid poured on imme- 

 diately. Therefore, in two or three seconds after the centrifugal 

 force had ceased to act the eggs were submitted to the action of 

 the killing fluid. Such eggs were sectioned and stained. 



The cases that interest us most here are those in which the 

 spindle is found detached from the surface, because it is obvious 

 that such spindles have been moved from their original position : 

 The entire karyokinetic figure in such cases may be perfectly 

 symmetrical if it is found in protoplasm of uniform composition. 

 But differences in the composition of the protoplasm within the 

 area of the karyokinetic figure are correlated with asymmetries 

 of the figure itself which are considered beyond. If the outer 

 pole of the spindle is withdrawn from the surface it is found to 

 possess well-developed antipolar rays, although these were en- 

 tirely wanting before centrifuging (cf. Fig. 5), and the astral rays 

 are symmetrical around both poles, although " organic radii ' 

 would naturally be distorted by such displacement of the " cen- 

 ters of insertion" as is illustrated in Fig. 5. It appears to me 

 that the astral radiations in such cases must be regarded as new. 

 The case is of course analogous to the shifting of sperm asters 

 in fertilization. In the present case, however, we know the time 

 of readjustment to be very short, one minute at the outside, and 

 the initial and reconstructed conditions are before us for com- 

 parison (cf. Figs, i and 5). 



Similar cases, are numerous in eggs that have been submitted 



