MENDELISM AND OTHER METHODS OF DESCENT 207 



and habitat which the section afforded. In some places the 

 normal type was more abundant, in others the mutant, while in 

 still other spots both were present in about equal numbers, 

 growing together closely intermingled. . . . 



'* This mutant is not of hybrid origin. Hybrids between certain 

 species of Verbena are common but are easily recognized from 

 morphological characters. No hybrids were found in the 

 locality. A careful search was made in all directions. . . ."' 



A new character is obviously analogous to a mutation, though 

 it does not behave as mutations are supposed to do. At present 

 it seems to have brought about a condition of dimorphism in the 

 parent species, instead of requiring to be isolated in order to be 

 preserved, though the possibility of segregation by some form 

 of reproductive incompatibility is not absolutely excluded. 



Sufcr sexual Dimoi'fhisni. — Similarly definite diversities of 

 color are also known among sexually higher differentiated ani- 

 mals, and may be reckoned as constituting still another method 

 of descent, supersexual dimorphism. The present interest of 

 this phenomenon lies in the fact that it proves that polarities of 

 expression may be maintained even in sexually differentiated 

 species and under conditions of free interbreeding. The diver- 

 sities of eye-color in the European races constitute a mild form 

 of such a dimorphism or alternative inheritance phenomenon, 

 as shown by the studies of Galton. 



Diversity in Social Organisms {Politisni). — Politism is a 

 method of descent in which a part of the offspring regularly 

 show characters different from any of their parents or ancestors, 

 accompanied by a deficient development of the sexual organs 

 and powers of reproduction, as in the highly socialized groups 

 of insects, such as the ants and the termites. Politism differs 

 from other kinds of dimorphism in that the offspring represent 

 from one to four specialized sterile castes, in addition to the 

 reproduction of the unspecialized sexual types. 



Character-transmission is here completely divorced from char- 

 acter-expression, for the sexual insects never express the char- 

 acters transmitted to the sterile castes, nor do the sterile castes 

 propagate their own characters or those of their parents. That 



'Schaffner, J. H., 1906. A Successful Mutant of Verbena Avithout External 

 Isolation. Ohio Naturalist, 7 : 31. 



