SYNAPSIS IN THE EGG OF THE WHITE RAT 445 



blocks of irregular size and shape (figs. 2, 3, and 4) which are dis- 

 tributed over the inner side of the nuclear membrane. The out- 

 line of the blocks is clear cut and definite. A few linin threads 

 may be attached to one or more of the blocks at this stage (figs. 

 3 and 4) . As in the case of the late telophase nuclei, here, too, the 

 preleptotene nuclei are evidently intimately associated in pairs, 

 as is clearly proved where remnants of interzonal fibers and 

 zwischenkorper persist between the cells of two such nuclei. 

 It may be concluded then that the late telophase nuclei increase 

 in size and become more spherical; and at the same time the 

 chromatin blocks separate and become arranged about the inner 

 surface of the nuclear membrane. In the early stages the num- 

 ber of these blocks of chromatin varies from twenty-two to 

 thirty-five and seems therefore not to be significant, except in 

 indicating a fragmentation of the original chromatin masses. 



The comparatively simple condition of the contents of the 

 nucleus represented by the peripherally arranged chromatin 

 blocks changes gradually into an extremely complex, chromatin- 

 linin network dispersed more or less regularly throughout the 

 entire nucleus. The changes represented by these closely simi- 

 lar conditions involve a regularly progressive increase in the 

 number of chromatin blocks, a gradual augmentation of the 

 number and complexity of arrangement of the linin threads, 

 and a more or less equal distribution of the chromatic material 

 throughout the entire nucleus, (figs. 4, 5, and 6). In the earlier 

 phases of this series of changes it may be readily seen that all of 

 the linin threads are attached to chromatin bodies, or, that the 

 many small, almost powdery particles of chromatin are arranged 

 along linin threads. There is no distinct chromatin element con- 

 stant in size or shape throughout this series of changes. 



This whole series of changes, from the very first form of the 

 primary oocytes to the most complex condition of the chromatin- 

 linin network, is strongly suggestive of the migration of chroma- 

 tin along linin filaments which later probably become incorpo- 

 rated in the leptotene threads. It is very difficult to explain in 

 any other manner the gradual decrease in average size and the 

 increase in number of the chromatin blocks, simultaneously with 



