MELANIN COLOR FORMATION. 345 



maturation divisions. It may for the present be assumed, and 

 this is, I think, all that is really demanded in accounting for the 

 differences in end-result in color development and inheritance - 

 that the germ cells vary in "strength," i. e., in such general 

 powers as assimilation, growth, oxidation, etc. (and this proposi- 

 tion is not all assumption) ; this general difference of " strength" 

 of germ cells may (or may not) arise during the maturation 

 divisions ; one or more of the four cells receiving in some species, 

 though not in all, a type of protoplasm in better or worse condi- 

 tion than the others --influenced, for example, by more or less 

 yolk ; yolk more or less affected by previous nuclear and cyto- 

 plasmic contact ; by variable distribution of the protoplasm of the 

 astrosphere ; by variable admixtures of nuclear (not necessarily 

 chromatin) and cytoplasmic matter ; by receiving more or fewer 

 entire chromosomes, etc. (Chromatin is well known to be a very 

 reactive substance and we may very well believe that wide varia- 

 tions of it in amount influence the vigor or intensity of vital proc- 

 esses occurring in a cell and in its derivatives ; but in this respect 

 chromatin is not unique, the other variables just mentioned doubt- 

 less do the same.) Any or all of these things will influence the 

 development of a character only by serving to strengthen or 

 weaken some process which underlies its formation. 1 



Such general differences of germ cells as arise from the several 

 possible causes mentioned above would conceivably tend to affect 

 the strength of such a general process as oxidation such as 

 produces scales of color. From the nature of these differences 

 it will be seen that the growth and maturation stages may occa- 

 sionally among organisms constantly perhaps in some forms - 

 furnish the conditions for the production of four sister sperm 

 cells of unequal strength, one or two may be especially favor- 



1 It is perhaps well in our estimation of the basis for segregation of color characters, 

 which rest directly on an oxidation process, to call attention to the special significance 

 of the centrosome and cytaster. Considerable evidence is adduced by Mathews ('07) 

 to show that the centrosome is the reduction center of the cell. Jf this should prove 

 true, very obviously our estimation of the oxidation powers of the cell would be better 

 treated in relation to this body than to any other in the cell. It cannot be too much 

 emphasized, "however, that upon this view the centrosome and the sphere is but a 

 region where intense reduction occurs ; the intensity grading oft from centriole to 

 (presumably) the periphery of the cell ; and this region should be thought of as an 

 expression of general powers of the whole cell. 



