34 The Selection Theory 



bees the Lamarckian factor may be excluded altogether, for it can 

 be demonstrated that here at any rate the effects of use and disuse 

 cannot be transmitted. 



But if it be asked why we are unwilling to admit the cooperation 

 of the Darwinian factor of selection and the Lamarckian factor, since 

 this would afford us an easy and satisfactory explanation of the 

 phenomena, I answer : Because the Lamarckian principle is 

 fallacious, and because by accepting it we close the ivay towards 

 deeper insight It is not a spirit of combativeness or a desire for 

 self-vindication that induces me to take the field once more against 

 the Lamarckian principle, it is the conviction that the progress of 

 our knowledge is being obstructed by the acceptance of this fallacious 

 principle, since the facile explanation it apparently affords prevents 

 our seeking after a truer explanation and a deeper analysis. 



The workers in the various species of ants are sterile, that is 

 to say, they take no regular part in the reproduction of the species, 

 although individuals among them may occasionally lay eggs. In 

 addition to this they have lost the wings, and the receptaculum 

 seminis, and their compound eyes have degenerated to a few facets. 

 How could this last change have come about through disuse, since 

 the eyes of workers are exposed to light in the same way as are those 

 of the sexual insects and thus in this particular case are not liable to 

 "disuse" at all? The same is true of the receptaculum seminis, which 

 can only have been disused as far as its glandular portion and its 

 stalk are concerned, and also of the wings, the nerves tracheae and 

 epidermal cells of which could not cease to function until the whole 

 wing had degenerated, for the chitinous skeleton of the wing does 

 not function at all in the active sense. 



But, on the other hand, the workers in all species have undergone 

 modifications in a positive direction, as, for instance, the greater 

 development of brain. In many species large workers have evolved, 

 the so-called soldiers, with enormous jaws and teeth, which defend 

 the colony, and in others there are small workers which have taken 

 over other special functions, such as the rearing of the young Aphides. 

 This kind of division of the workers into two castes occurs among 

 several tropical species of ants, but it is also present in the Italian 

 species, Colobopsis truncata. Beautifully as the size of the jaws 

 could be explained as due to the increased use made of them by the 

 "soldiers," or the enlarged brain as due to the mental activities of 

 the workers, the fact of the infertility of these forms is an insur- 

 mountable obstacle to accepting such an explanation. Neither jaws 

 nor brain can have been evolved on the Lamarckian principle. 



The problem of coadaptation is no easier in the case of the ant 

 than in the case of the Giant Stag. Darwin himself gave a pretty 



