SUMMARY 215 



her to destroy the yonnpf queens, her daughters, as soon as 

 they are born, or to perish herself in the combat; for un- 

 doubtedly this is for the good of the community ; and mater- 

 nal love or maternal hatred, though the latter fortunately is 

 most rare, is all the same to the inexorable principle of 

 natural selection. If we admire the several ingenious contri- 

 vances, by which orchids and many other plants are fertilised 

 through insect agency, can we consider as equally perfect 

 the elaboration of dense clouds of pollen by our fir-trees, so 

 that a few granules may be wafted by chance on to the ovules? 



summary: the law of unity of type and of the 



conditions of existence embkaced by the 



theory of natural selection 



We have in this chapter discussed some of the difficulties 

 and objections which may be urged against the theory. 

 Many of them are serious ; but I think that in the discussion 

 light has been thrown on several facts, which on the belief 

 of independent acts of creation are utterly obscure. We have 

 seen that species at any one period are not indefinitely vari- 

 able, and are not linked together by a multitude of interme- 

 diate gradations, partly because the process of natural selec- 

 tion is always very slow, and at any one time acts only on a 

 few forms ; and partly because the very process of natural 

 selection implies the continual supplanting and extinction 

 of preceding and intermediate gradations. Closely allied 

 species, now living on a continuous area, must often have 

 been formed when the area was not continuous, and when the 

 conditions of life did not insensibly graduate away from one 

 part to another. When two varieties are formed in two dis- 

 tricts of a continuous area, an intermediate variety will often 

 be formed, fitted for an intermediate zone ; but from 

 reasons assigned, the intermediate variety will usually exist 

 in lesser numbers than the two forms which it connects: con- 

 sequently the two latter, during the course of further modi- 

 fication, from existing in greater numbers, will have a great 

 advantage over the less numerous intermediate variety, and 

 will thus generally succeed in supplanting and extermi- 

 nating it. 



