276 CONCLUDING EEMAKKS Chap. VI. 



powers. We shall, perhaps, best perceive the complex 

 and extraordinary nature of the marriage arrangements 

 of a trimorphic plant by the following illustration. 

 Let us suppose that the individuals of the same species 

 of ant always lived in triple communities; and that 

 in one of these, a large-sized female (differing also in 

 other characters) lived with six middle-sized and six 

 small-sized males ; in the second community a middle- 

 sized female lived with six large- and six small-sized 

 males ; and in the third, a small-sized female lived 

 with six large- and six middle-sized males. Each of 

 these three females, though enabled to unite with any 

 male, would be nearly sterile with her own two sets of 

 males, and likewise with two other sets of males of the 

 same size with her own which lived in the other two 

 communities ; but she would be fully fertile when 

 paired with a male of her own size. Hence the thirty- 

 six males, distributed by half-dozens in the three com- 

 munities, would be divided into three sets of a dozen 

 each; and these sets, as well as the three females, 

 would differ from one another in their reproductive 

 powers in exactly the same manner as do the distinct 

 species of the same genus. But it is a still more 

 remarkable fact that young ants raised from any one 

 of the three female ants, illegitimately fertilised by a 

 male of a different size would resemble in a whole 

 series of relations the hybrid offspring from a cross 

 between two distinct species of ants. They would be 

 dwarfed in stature, and more or less, or even utterly 

 barren. Naturalists are so much accustomed to behold 

 great diversities of structure associated with the two 

 sexes, that they feel no surprise at almost any amount 

 of difference ; but differences in sexual nature have 

 been thought to be the very touchstone of specific 

 distinction. We now see that such sexual different-ea 



