OTHER FACTORS OF EVOLUTION 125 



the production of a queen bee rather than a neuter according to 

 the kind and amount of food given to the larva ; and secondly, in a 

 communication quoted by H. Spencer (I, p. 687), from the Superin- 

 tendent of the Royal Botanic Gardens in Trinidad concerning what 

 are known as ' Parasol ' ants, it is said that by different modes 

 of feeding " ants can practically manufacture at will, male, female, 

 soldier, worker, or nurse " ; while the same authority adds, " Some 

 of the workers are capable of laying eggs, and from these can 

 be produced all the various forms as well as from a queen's egg." 



We must turn now to the different cases cited by Herbert 

 Spencer during the celebrated discussion that took place between 

 him and Weismann in the pages of The Contemporary Review 

 in 1893-4, his contributions to which are reproduced as an 

 Appendix to the first volume of " The Principles of Biology." An 

 admirable resume of his own point of view will be found in his 

 fourth article (pp. 671-695), so that only brief references to the 

 principal instances cited will be mentioned here. One of the most 

 weighty has reference to the co-adaptation of co-operative parts 

 in reference to use-inheritance. He cites, for instance, the case of 

 the extinct Irish elk, the male of which had enormously developed 

 horns, weighing upwards of a hundredweight, " carried at great 

 mechanical disadvantage : supported as they are along with the 

 massive skull which bears them, at the extremity of the outstretched 

 neck." Moreover, " that these heavy horns may be of use in 

 fighting, the supporting bones and muscles must be strong 

 enough, not simply to carry them, but to put them in motion 

 with the rapidity needed for giving blows. Let us then ask how, 

 by natural selection, this complex apparatus of bones and muscles 

 can have been developed pari passu with the horns ? ... It 

 would be a strong supposition that the vertebrae and muscles of 

 the neck suddenly became bigger at the same time as the horns. 

 It would be a still stronger supposition that the upper dorsal 

 vertebrae not only at the same time became more massive, but 

 appropriately altered their proportions, by the development of 

 their immense neural spines. And it would be an assumption still 

 more straining our powers of belief, that along with heavier horns 

 there should spontaneously take place the required strengthenings 

 of the bones, muscles, arteries, and nerves of the scapula and 

 the fore-legs" (pp. 537-8). Through the intermediation of the 

 inherited effects produced by use all the co-operative parts could 



