98 GARDINER. [Vol. XV. 



in the very substance which so quickly dissolves and assimilates 

 the rest of the nucleus, there seems no escape from one or the 

 other of the above conclusions. 



Again, in the cleavage spindle the chromosomes remain prac- 

 tically unaltered for days (p. "]"]), while the enormous nuclear 

 chromatin once scattered through the cytoplasm dissolves in 

 a very short time. We cannot, therefore, but conclude that 

 they must differ chemically, or else that the achromatic rays 

 or some other substance builds around the chromosomes a wall 

 protecting them from the attacks of the dissolving agents in the 

 cytoplasm. The greater portion of the clumps or rods of chro- 

 matin described above must have the same structure as the 

 bulk of the nucleus, for they also are dissolved, though more 

 slowly, and only the chromosomes are left. Since it thus 

 appears that the substance of the chromosomes differs from 

 that of the rest of the chromatin of the nucleus in being insol- 

 uble, there are three possibilities presented as to the manner 

 in which this difference may have arisen : — First: that two 

 distinct chromatic substances have existed prior to the spindle 

 formation, one soluble and the other insoluble ; the former des- 

 tined to be formed into chromosomes bearing the hereditary 

 traits, and the other, food for the cytoplasm. Second: that 

 there is but one chromatic substance in the nucleus, and that 

 this is soluble in the cytoplasm ; as the spindle is formed cer- 

 tain particles are changed into insoluble stuff from which the 

 chromosomes are formed ; with the breaking down of the 

 nuclear wall the rest of the chromatin is exposed to and dis- 

 solved by the cytoplasm. Third: there is but one chromatic 

 substance in the nucleus and that this substance is insoluble 

 in the cytoplasm ; of this substance the chromosomes are 

 formed ; the rest undergoes chemical degeneration and be- 

 comes soluble in the cytoplasm. 



Now to consider these three propositions in the order stated 

 above. If we accept the first, we must assume that some 

 force causes a migration of the insoluble rather than the sol- 

 uble particles toward the center of the nucleus to be formed 

 into clumps. This migration, however, if it occur, does not 

 visibly disturb the structure of the rest of the nucleus. On 



