I2 THE EVOLUTION OF SEX. 



of a forthcoming volume; but the general conclusion of the naturally 

 greater variability of the males will be stated in a different light toward 

 the close of the following chapter. It will there be shown that the 

 " something within the animal " which determines the preponderance 

 of male variability may be stated in simpler terms than are involved in 

 Brooks's theory of heredity. To refer preponderant male variability 

 back to a power, ascribed to the male reproductive cells, o{ collecting 

 and storing up assumed gemmules, is at best but a halfway analysis. 



Both the above critics are at one with Darwin on essential points. 

 Though Wallace would explain by natural selection what Darwin 

 explained by sexual selection, he does not deny the importance of the 

 latter in many cases. Brooks, again, emphasizes a deeper factor, 

 without doubting the general truth of Darwin's account of the process. 

 Different from both these positions is that occupied by (V) St. George 

 Mivart, who looks for some deeper reason than either Darwin or 

 Wallace suggests. The entire theory of sexual selection appears to 

 him an unverified hypothesis, only acquiring plausibility when 

 supported by quite a series of subsidiary suppositions. He submits 

 a number of detailed criticisms; but his chief contention is that the 

 beauty of males, and other secondary sexual characters, are not the 

 indirect results of a long process of external selection, but the direct 

 expressions of an internal force. 



The vague suggestions of Mantegazza and others are only ol 

 importance as indications of progress toward a fundamental explana- 

 tion. An obvious objection to the theory of sexual selection, that 

 has been urged by many, is that, while it may in part account for 

 the persistence and progress of secondary characters after they 

 attained a certain degree of development, it does not account for their 

 preservation when weak or inconspicuous; in short, the theory may 

 account for the perfecting but not for the origin of the characters. It 

 may be enough to account for the length and the trimmings of the 

 living garment, but what we wish to know is the secret of the loom. 

 Darwin's account of the evolution of the eyes on the feathers of the 

 argus-pheasant is indeed ingenious and interesting; but, whatever its 

 probability, it is more important to ask what the predominant 

 brightness of males means as a general fact in physiology. It is of 

 interest, then, to notice the hints thrown out by Mantegazza, Wallace, 

 and others, directly associating decorativeness with superfluous repro- 

 ductive material, and the putting on of wedding-robes with the 

 general excitement of the sexually mature organism. From this 

 record of the discussion, it is time, however, to turn to a more 

 constructive mode of treatment. 



