456 THE AMEBIC AN NATURALIST [Vol. XLIV 



gested by Hertwig and held also by others, especially by 

 Fick, that the formation of the chromosomes and of the 

 network represents a kind of crystallization process that 

 is regulated by the amount of chromatin present. This 

 suggestion also meets with serious objections, for, were 

 it true, we should expect, I think, to find that the chromo- 

 somes would assume definite positions with regard to 

 each other. The evidence shows clearly that this is not 

 the case, as seen best when chromosomes of different 

 sizes exist. The arrangement is varied in different cells 

 of the same individual and in only a few cases do certain 

 chromosomes lie in a definite position in the equatorial 

 plate — in the center of the plate, for example, as seen in 

 the spermatocyte divisions of certain insects. We can 

 only fall back, therefore, on the evidence, brought for- 

 ward by Eabl and demonstrated in the clearest way by 

 Boveri, showing that the position of the chromosomes in 

 the new division is determined by the position of the 

 chromatin in the last division, and assume that in some 

 way the center of the old chromosomes becomes the cen- 

 ter of the new. 



Putting the facts together, they go far towards show- 

 ing that the central axis of the chromosome is not lost in 

 the resting nucleus, but remains to become the center of 

 the next chromosome. Here perhaps we find a clue to the 

 genetic continuity, or individuality. If we look upon 

 the spinning process of the chromosome as a process by 

 means of which its peripheral substance is thrown out 

 into the nucleus to form the reticulum, and assume that 

 most of it fails to return the next time the chromosome 

 becomes distinct, we have an hypothesis in conformity 

 with many facts at least, and also a view that makes 

 simpler, perhaps, our interpretation of the meaning of 

 the process. On this view the materials set free by the 

 chromosomes remain behind in part when the nuclear 

 wall is dissolved, and become a part of the cytoplasm of 

 the cell. In this way chromatin materials set free at 

 each breaking down of the nucleus reach the cytoplasm, 

 and in time may come to represent a large part of the cy- 



