Social Insects. 57 



my own writings.* The tendency to such production was doubt- 

 less developed in the ancestors of the present species, and Ave may 

 even trace the steps by studying the gradations in existing species. 

 The facts connected with the social insects Avhiqli I have con- 

 sidered, present the strongest argument in favor of the heredity 

 of acquired characters and tendencies. Competition has been 

 between colonies rather than individuals, and those colonies 

 which have acquired, through heredity, the habit of producing, 

 through one or more fertile females, the different forms which 

 have proved useful in the social economy, have, in the course of 

 time, survived others in which such tendency was less pro- 

 nounced. Yet various steps in the process are yet manifest 

 in the different species, and under these circumstances it seems 

 to me foolish to insist that the fixed habit in one species 

 has, per sc, any especial advantage over the less fixed habit 

 in others which still maintain themselves. I need hardly 

 say to the members of this Society who are familiar with my 

 views as to the causes of variation, that it does not follow in 

 my mind that the different forms of Termites, for instance, that 

 are found in the colonies of some species, are all essential, but 

 that some of the forms may be advantageous, others only par- 

 tially so, and still others purely fortuitous. The tendency to 

 vary — an inherent property in all organisms — has shown itself 

 among the individuals of tiiese different colonies. These 

 variations have been guided by natural selection among col- 

 onies, and by what I have just referred to as social selection 

 among individuals, along certain lines which are most useful. 

 In other cases the variation has accumulated along lines of 

 secondary utility ; while in yet others it has gone along lines 

 Avhich are purely fortuitous and still most variable and unfixed — 

 natural selection playing little or no part in these. In species 

 with the less complete social organization, the existing variations 

 will be greatest; while the structures and functions have become 

 most fixed and show least tendency to vary in those species which 

 have become most specialized and perfect in their social economy. 

 It is very questionable, however, whether, in the struggle for ex- 

 istence, this greater specialization and fixity give the species any 



*See more particularly the address before Section F, at the Cleveland 

 (1888) meeting of the A. A. A. S , and the paper before this Society "Oa 

 the interrelations of Plants and Insects," Vol. VII, pp. 81-104 (May, 1892). 



