68 NATURE OF DISCONTINUITY. [introd. 



The best known instance of this is that of gynandromorphic 

 insects, in which the characters of the whole or part of one side 

 of the body, wings and antennae, are male, while those of the 

 other side are female. Remarkable instances of a similar pheno- 

 menon have been recorded among bees and will be described later. 

 As is well known, the organs and especially the legs of the sex- 

 less females or workers are formed differently from those of the 

 drones, but there are cases of individuals having some of the 

 parts and appendages formed on the one plan arid some on the 

 other. Thus in these individuals, which are in a sense inter- 

 mediate between workers and drones, the characters of the two 

 sexes may still be not completely blended, the male type pre- 

 vailing in some parts, and the female in others. In the Dis- 

 continuity of Substantive Variation will be found examples of 

 imperfect blending of variety and type closely comparable with 

 this case of the imperfect blending of Sex. 



SECTION XIII. 

 Suggestions as to the natuke of Discontinuity in Variation. 



The observations at the end of Section XI, regarding the Dis- 

 continuity of Meristic Variation lead naturally to certain reflexions 

 as to the nature of Discontinuous Variation in general. In tin- 

 case of the Cockroach tarsus, there given, it appeared that just as 

 the structure of the typical form varies about its mean condition, 

 so the structure of the variety varies about another mean condition. 

 This fact, which in the given instance of Meristic Variation is so 

 clear, at once suggests an inquiry whether this is not the usual 

 course of Discontinuous Variation, and, indeed, whether Discon- 

 tinuity in Variation does not mean just this, that in varying the 

 organism passes from a form which is the normal for the type to 

 another form which is a normal for the variety. Such transitions 

 plainly occur in many cases of Meristic Variation, and in a consider- 

 able number of Substantive Variations there will be found to be 

 indications that the phenomenon is similar. It is true that at the 

 present stage of the inquiry the evidence has the value rather of 

 suggestion than of proof, but the suggestion is still very decided 

 and it is scarcely possible to exaggerate the importance of even 

 this slender clue. 



In stating the problem of Species at the beginning of this 

 inquiry it was said that the forms of living things, as we know 

 them, constitute a discontinuous series, and it is with the origin 

 of the Discontinuity of the series that the solution of the main 

 problem is largely concerned. Now the evidence of Discontinuous 

 Variation suggests that organisms may vary abruptly from the 



