170 Heredity. 



Darwin has gone over the whole field so thoroughly 

 and exhaustively that little remains to be said ni)on the 

 subject, and the reader who is familiar with the essay 

 will discover that almost all the facts in this chapter are 

 borrowed from this source. 



Darwin's aim, however, is simply to show the potency 

 of sexual selection, while our present object is to show 

 the frequency of hereditary male modification as com- 

 pared with female modifications, and I have there- 

 fore rearranged the facts, so as to give especial promi- 

 nence to this aspect of the subject. The critical reader 

 will discover that in many cases I have borrowed the 

 descriptive portion of one of Darwin's paragraphs, but 

 have said nothing about the theoretical portion. As 

 Darwin's conclusions are in many cases opposed to my 

 own, this may convey to some the impression that I 

 have made an unfair use of the weight of his authority, 

 and have quoted him in support of conclusions which 

 he in reality opposes. I will refer such readers to the 

 chapter which follows this, where I have devoted a sec- 

 tion to a statement of Darwin's view of the origin of 

 secondary sexual characters, and have given my reasons 

 for believing that it is only a partial explanation of the 

 phenomena in question. 



Examples from Various Groups of the Animal Kingdom 

 to show that in all Groups where the Sexes are Sepa- 

 rate the 3Iale is, as a Rule, more Modified than the 

 Female, and that the Adult Males of Allied Species 

 differ more, as a Rule, than the Females or Young. 



RoTiFERA. — In 1849, Dalrymple (Description of an 

 Infusory Animalcule allied to the Genus Notommata, 

 Phil. Trans. 1849) made the interesting and remarkable 

 discovery that, in one species of the Rotifera, Notom- 



