266 



LILLIE. 



[VOL. I. 



substance of the inner sphere is quite dense, and takes the 

 red stain (Bordeaux red) strongly. 



c. The radiating fibers are simply an arrangement of the 

 cytoplasmic network, with all that this implies. 



d. Microsomes are found on all fibers of the asters and of 

 the spindle, with the possible exception of the central spindle. 

 They are certainly least conspicuous on the central spindle. 



In the late antiphase of tJic first maturation swindle the cen- 

 trosome has divided into two, and the inner sphere is bounded 

 by a continuous membrane, into which the central ends of the 



FIG. i. First Maturation Spindle of Unio. 



FIG. 2. Horizontal Section through the 

 Outer Aster of the First Maturation 

 Spindle of Unio in the Stage of Fig. i. 



rays are inserted. This membrane (cf. Fig. 6) is produced in 

 part by the fusion of the inner stratum of microsomes, but 

 chiefly by the peripheral accumulation of the ground sub- 

 stance of the inner sphere. The substance of the mantle 

 fibers is heaped up in the cortical zone, and the fibers of the 

 central spindle exhibit large, deeply staining microsomes. 



In the early telopliasc of the first maturation spindle the cen- 

 trosomes are extremely large, and each is composed of a group 

 (at least four) of densely black granules. The ccntrosomcs arc- 

 united to the membrane of the inner sphere by a few irregular 

 threads which are not part of the system of radiations (cf. Fig. 6). 

 The rays of the aster and the fibers of the central spindle are 

 studded with enormous closely set black microsomes, the inter- 

 vening substance staining faintly in Bordeaux. 



