RELATION OF TRUE NUCLEOLUS TO LININ NETWORK. 125 



amount of plasma substance is so small in comparison with the 

 embedded chromatin, that the latter acts as the governing factor 

 in determining the shape of the whole mass; but by the time 

 the stage under consideration (Figs. 17 to 20) is reached, the 

 achromatic part of the nucleolus is sufficiently large to be only 

 slightly affected by the presence of the embedded bodies. How- 

 ever, in cases where the nucleolus has a slight irregular contour, 

 the same can usually be accounted for by the presence of one or 

 more of the sex-chromosomes near the periphery. 



The nucleus now has a period of very rapid growth accom- 

 panied by noticeable extra-nucleolar changes. In the earlier 

 stages the nucleus presents a somewhat uniform fibrillar but 

 granular appearance, though much darker near the nuclear 

 membrane than in the central part. The clear area around the 

 nucleolus increases in size and, in the middle growth period, 

 shows no traces of linin. As the cell continues to grow the linin 

 becomes more compact, first near the nuclear wall and then 

 nearer and nearer the nucleolus (Figs. 16 to 20). Numerous 

 instances may be seen where entanglements of linin are scattered 

 indiscriminately throughout the nucleus even into the vacuole- 

 like space. 



At a little later stage this whole complex mass between the 

 nucleolus and nuclear wall, presents the appearance of innumer- 

 able anastomosing threads of a fibrillar substance, in which are 

 embedded minute granules. These fibers continue to elongate 

 until they come in contact and ultimately fuse with the true 

 nucleolar portion of the nucleolus. This fusion, together with 

 a continued growth on the part of both the true nucleolus and 

 the surrounding linin, causes the two to become continuous and 

 to assume a similar appearance (Figs. 22 and 23). Prior to this 

 time the achromatic part of the nucleolus has presented a typical 

 homogeneous appearance, but as more granular fibers come in 

 contact and fuse with it, it assumes a more granular appearance 

 (Figs. 21-25). The achromatic part of the nucleolus now greatly 

 resembles the granular appearance shown in the stages prior to 

 the individualizing of the sex-chromosomes. This condition 

 suggests that chromatin granules have moved along the linin 

 and entered the true nucleolus. This indicates that the plasmo- 



