ASPECTS OF KINETIC EVOLUTION 371 



Subsexual Species. — A species consisting of bisexual organ- 

 isms divided into subsexes, that is, into groups differing in one 

 or more characters, but not showing special adaptations to 

 secure cross-fertilization. 



The first stage of specialized heterism is represented by spe- 

 cies which include two or more types or forms, merely for the 

 sake of the diversity, as it were, and with no sexual diversifi- 

 cation, that is, no adaptations, for securing cross-fertilization 

 between the two forms. The differences appear to be of the 

 same nature and to have the same symbasic utility as secondary 

 sexual characters, but the utilization of them is still left to 

 chance. Examples of subsexes are probably to be found in 

 such species as Verbascum blatlaria, Viola hicolor, and others 

 in which plants of different castes live together indiscriminately. 

 Antidromous or right-and-left-handed plants like cotton and 

 Casltlla, might also be recognized as affording instances of 

 subsexual differentiation. 



It often happens in zoology that the sexes of the same animals 

 are at first described and named as two distinct species, but 

 after their true relations have been ascertained one of the sup- 

 posed species is, of course, rejected, no matter how diverse the 

 sexes may be. Similarly, these subsexual forms need to be 

 taken into account by the taxonomist. The criteria commonly 

 applied to determine specific distinctness are not adequate, since 

 it is possible for constant differences unconnected with sexual 

 diversity, to exist inside the same species without in any way 

 justifying the taxonomic subdivision of the group on the usual 

 basis. There is, however, no reason why any established type 

 of diversity like these subsexes should not be named and de- 

 scribed separately, just as the sexes are treated separately when 

 their characters are different. 



Botanists are acquainted with numerous instances of diversity 

 among the members of species which may prove to be subsexes ; 

 though it is also possible that the differences may belong to 

 species which closer study may distinguish. Thus there are 

 species of Actcea which have the berries either waxy white or 

 crimson, and in about equal quantities. Numerous species of 

 Delphinium have the flowers either pink or blue. In species 



