22 MARGARET C. FERGUSON 



botanists, and many zoologists consider it a definite characteristic 

 of the early prophase of the heterotypic mitosis, several of these 

 investigators having noted it in their material before fixation. I 

 have observed this stage in the fresh material in Pinus, and 

 after carefully studying it in many permanent preparations, I 

 see no reason why this condition, simply because it happens to 

 be one of contraction of the nuclear substance, should be set 

 down as abnormal. 



If this appearance were produced artificially why should 

 there be transitional forms both in leading up to and in recovery 

 from it? If it were the result of diffusion currents, as has been 

 suggested, we should expect to find the nuclear substance in 

 all the nuclei of a given anther carried or forced to the same 

 side of the nuclear cavity, but such is not the case. It is doubt- 

 less true, as indicated by Strasburger ('95), that many phenom- 

 ena described as synapsis represent pathological conditions 

 which do not occur under all circumstances, but it seems equally 

 true that this condition of the nuclear substance represents, in 

 some species at least, a characteristic stage in the heterotypic 

 division. Although a contraction comparable with that of 

 synapsis has been reported for somatic cells, I am not aware 

 that anything like so marked an appearance has been described 

 as a usual accompaniment of any but the heterotypical division. 

 The exact significance of this phase is not well understood, 

 but that it is intimately associated with a readjustment of the 

 chromatic and nucleolar substances there can be little doubt. 



As the nucleus slowly recovers from synapsis, it soon becomes 

 apparent that the reticular structure has been replaced by a broad, 

 closely coiled band which stains more deeply than did the net- 

 work prior to the contracted stage. The coils of the thread 

 gradually open out until the nuclear cavity is filled with a 

 spireme, which consists of a broad linin band, so irregularly 

 studded with chromatin-granules that it has a much roughened, 

 almost minutely echinulate, appearance. These granules soon 

 collect into indefinitely outlined masses which remain connected 

 by clear, faintly staining portions of the linin thread. The chro- 

 matin-groups never assume the definite disk-like form figured by 

 Mottier ('97) for Lilium and Helleborus, and by Duggar ('oo) 



