1 9 1 q] STOV T—IN TERSEXES 1 2 5 



hybridization, and from that steriHty ascribed to replacement of 

 sexual reproduction by asexual means (Gates and Goodspeed g), 

 in both of which the tendency is to give a very uniform impotence 

 of both sexes. A high degree of impotence is present in many 

 plants regarded as pure species. Jeffrey (14, 15, 16) has recently 

 emphasized the view that such sterihty is to be considered as 

 conclusive evidence of hybrid origin. Intersexuality, however, 

 involves much impotence, and may very clearly develop in pure 

 species through lability of the processes of sex determination. 



At this point one may well inquire whether differences in sex- 

 uality somewhat akin to intersexuality may be present in species 

 that are morphologically fully hermaphrodite, and in which no 

 appreciable impotence of sex organs is in evidence. For example, 

 Darwin reports that plants of "the short-styled form of Primula 

 veris produce more seed than the long-styled in the proportion of 

 nearly four to three (7, p. 19), and that in Lythrum Salicaria (6, 7) 

 the mid-styled form is potentially capable of higher seed produc- 

 tion than plants or either of the other two forms. Judged on the 

 basis of seed production, certain forms in heterostyled species 

 appear to be more female than others. Sexuality of species as 

 such is obviously more intense in some than in others if we are 

 to judge by seed reproduction. Much variation in total seed 

 production is seen among races and among individuals of a race. 

 Such considerations raise many questions regarding the determina- 

 tion of potentiality of sex reproduction through production of 

 seed, and most especially of the relations of vegetative to repro- 

 ductive function. Undoubtedly much variation in maleness and 

 femaleness exists in sex organs that are morphologically perfect. 

 The sexual behavior of female pigeons has especially been studied 

 by Riddle as an index of the degree to which femaleness is devel- 

 oped. He states (22, p. 341) that "females hatched from eggs 

 laid earlier in the season are more masculine in their sex behavior 

 than are their own full sisters hatched later in the season. And 

 several grades of females can he thus seriated according to season of 

 hatching." 



The existence of physiological incompatibilities (Stout 25) 

 between sex organs that are fully formed, potentially functional, 



