436 WESLEY R. COE, 



chromatic substance comes into direct contact with the cytoplasm and 

 regains its strong affinity for nuclear stains. By this time, however, 

 it is no longer arranged in the form of a network, but has been 

 broken up into a mass of irregular granules (Fig. 7), and it is these 

 which stain blue with haematoxylin. This large mass of granules is 

 absorbed only very slowly into the general body of the cytoplasm, 

 although its boundaries soon become difficult to determine. This 

 nuclear matter occupies the region about the forming polar spindle, 

 and continues to surround it as it rotates to its definite position 

 (Fig. 9). The mass decreases in size and becomes less marked as 

 the second polar body is formed, although the region which it occupies 

 is distinguished from the rest of the cytoplasm by its deeper stain 

 nearly up to the time of the first cleavage. 



The linin "network" stains but very faintly, and it is difficult to 

 determine whether it actually consists of a distinct network of delicate 

 fibres, or whether the apparent network which is obtained in mounted 

 preparations is made up merely of the lines of coagulation of a 

 homogeneous protoplasmic substance which in life filled up the body 

 of the germinal vesicle , and in which the chromatic network is 

 suspended. The former view, however, seems to me the more prob- 

 able. 



The nucleolus may occupy any position in the nucleus. It usually 

 stains a deep red in Bordeaux-haematoxylin preparations. It measures 

 about 0,012 mm in diameter, and consists usually of an outer homo- 

 geneous layer with a more spongy interior. Not seldom, one or more 

 homogeneous, spherical bodies of various sizes are seen in its interior 

 (Fig. 13 a, b). These commonly stain like chromatin. At about the 

 time of the appearance of the asters of the polar spindle, one or 

 more vacuoles appear in the spongy substance of the nucleolus. When 

 more than one, these fuse together, and the larger vacuole thus formed 

 increases in size until it fills up the greater portion of the whole 

 nucleolus (Fig. 13 c, d, e). The large vacuole is situated eccentrically, 

 aod by its growth approaches the wall of the nucleolus on one side. 

 It finally breaks through and places the interior in communication 

 with the surrounding nuclear substance. The opening increases in 

 size by absorption of the nucleolar substance until only a cup-shaped 

 body remains (Fig. 13 f ). This gradually disappears, and the nucleolus 

 is entirely absorbed by the time the polar spindle is formed. In 

 Micrura caeca, on the other hand, the nucleolus disappears much 

 more slowly, and may often be seen lying in the cytoplasm of the 



