JOURNAL OF VARIATION. 



No. 9. Vol. VI. May 15th, 1895. 



On the development of ^eX in Social Insects. 



By J. W. TUTT, F.E.S. 



There is an article by Dr. St. George Mivart in the March 

 number of Harper's Moathly Magazine on " Heredity," in which, amono- 

 other things, the author criticises that j)art of Prof. Weismann's 

 Romanes Lecture, 1894, which deals with the development of sex in 

 " social insects." 



It is, of course, well known, that Lamarck, the French naturalist 

 antedated Darwin in the publication of the opinion that the develop- 

 ment of species was essentially due to modifications which were 

 brought about in existing species by the influence of chano-es in their 

 environment, and that such modifications were transmitted to their 

 progeny, and after a time l)ecame permanent. Darwin in part followed 

 out this idea in his Orlijia of Species, but, in addition, he worked out the 

 conception that these modifications, due to changed environment were 

 intensified and made perfect by "natural selection "; that, instead of 

 comparatively fixed characters, as it were, becoming modified, every 

 living organism or part of an organism was subject to indefinite varia- 

 tions, and that the destructive agencies at work in nature weeded out 

 individuals possessing characters that were disadvantageous so that 

 only iudividuals possessing such characters as were of advantao-e were 

 ju'eserved. These characters were transmitted by them to their off- 

 spring and, as the useful characters would vary indefinitely in diverse 

 organisms, the most different characters might l)e selected and trans- 

 mitted. The main point of Darwin's conception, then, was not so 

 much the acquisition of new charactei's to be handed down as the 

 modification of existing characters in a direction useful to the particular 

 individual — the handing down of such modified structures by 

 " heredity " being assumed as a matter of course. 



Every entomologist who has studied his insects knows how much 

 there is to be said for the existence of these congenital variations • 

 among Lepidoptera it may be truly said that no two insects have' 

 exactly the same facies. Now we know that tlie broad lines of 

 congenital variation can be transmitted to offspring (as \vitness the 

 racial breeding of Ainphidasi/s hetularia var. donb]edai/aria, Szc) and 

 therefore we can hardly deny that the smaller congenital variations are 



