496 ROBERT CHAMBERS, JR. 



a comparatively rigid body. It is gelatinous and somewhat 

 extensible. Figure 12 shows how it may be pulled about on the 

 cytoplasm dragging the poles of the amphiaster with it. The 

 extensibility of its substance is shown in figure 16. Figure 15 

 represents a maturation figure in the Cerebratulus egg. The 

 astral figure at the end of the 'spindle' directed toward the sur- 

 face of the egg adheres to the cell periphery. The other end lies 

 free in the liquid cytoplasm. In figure 16, the spindle is shown 

 pulled out and bent by a needle which has been inserted into one 

 end. On being released the spindle may slowly return to its 

 original shape. 



Spindle fibers have not been detected as morphological struc- 

 ture until death coagulation sets in. May they not be inter- 

 preted as strands produced by the coagulation of a hyaline sub- 

 stance in which, previous to coagulation, there existed lines of 

 stress or diffusion? 



In the telophase the nuclear mass becomes dumb-bell shaped 

 owing to a constriction around its middle. The constriction 

 deepens and broadens as the two halves of the nuclear body 

 draw away from one another and a strand connecting them does 

 not always break through until the cell itself has completed its 

 di\dsion. 



5. The aster in maturation figures 



This was studied in the Cerebratulus egg. The germinal 

 vesicle breaks down twenty minutes to half an hour after the 

 egg has been placed in sea water. Its place is taken by a clear 

 area in the granular cytoplasm which flows gradually in one 

 direction to the periphery of the egg spreading somewhat as it 

 goes. In this columnar or rather funnel shaped area appears 

 the first maturation spindle (fig. 14). As the spindle elongates 

 hyaline plasma collects on its two poles around which the astral 

 rays become more and more distinct while the cytoplasm be- 

 tween the rays passes into the gel state (fig. 15). The whole 

 structure, viz., asters and spindle, can be pulled and pushed 

 about causing the rays to form curves and spirals. If the dis- 

 tortion be not too great, the spindle will continue its normal 

 development irrespective of spirally curved rays which may or 



