1 90 APPENDIX II INTENSIVE SEGREGATION. 



of at least a portion of their ancestry, and the correlation of these 

 endowments must have been produced through the action of other 

 principles. 



The prevalence of males in times of pressure, with the prevalence of 

 females in times of plenty, is regarded by Dr. W. K. Brooks, of Johns 

 Hopkins University, as a characteristic established by natural selec- 

 tion, by which the organism acquires variability or fixity of type 

 according as either character is most needed; for according to his 

 observations the males represent the former and the females the latter 

 element. There can be no doubt that in many species the males are 

 more variable than the females, and that in some of the same species 

 the proportion of males increases with the degree of adversity; but 

 this does not seem to be sufficient ground for maintaining that the 

 increase in the proportion of males will increase the variability of 

 the offspring. Increase in the number or amount of the variable 

 element does not necessarily involve increase in the variability of 

 either element or in the offspring of both. I find need of additional 

 factors in order to bring these facts into any relation to the increase 

 of variability. Granting that the sperm-cell is the source of variation 

 and the germ-cell the source of fixity, and that increased tendency 

 to variation in the offspring will be secured by an increased range 

 of variation in the sperm-cells, it does not follow that increase in 

 the relative number of males will increase the range of variation in 

 the sperm-cells, and, therefore, in the offspring. But if conflict in the 

 environment and the winnowing process of natural selection falls 

 most heavily upon the males, there must be some advantage in having 

 their relative numbers increased in times of adversity; and if the 

 exposure of parents to hardships increases the variability of either 

 male or female offspring, and especially if it increases the variability 

 of both, plasticity will be increased. 



Professor Cope's "Doctrine of the Unspecialized " (Origin of the 

 Fittest, pp. 232-235) rests on the fact that the most highly specialized 

 types, as well as individuals, are most likely to be exterminated by 

 extraordinary changes in the environment; and Mr. Hyatt's "Tera- 

 tology" (Proceedings American Association, vol. xxxn, pp. 349-360) 

 teaches that types that are being slowly exterminated usually assume 

 forms resembling those produced by old age and disease in the indi- 

 vidual. These and other laws in the growth and decay of types 

 and individuals are of great interest, as they afford organic condi- 

 tions under which the factors of transformation must act. 



