INADEQUACY OF NATURAL SELECTION, ETC. 655 



state. It is to be inferred that if, after a certain stage of growth 

 has been reached, the food-supply becomes inadequate or is 

 stopped altogether, the larva undergoes its transformation pre- 

 maturely ; and, as we shall presently see, this premature trans- 

 formation has several natural sequences. 



Let us return now to the wasp's family history. In the spring, 

 a queen-wasp or mother-wasp which has survived the winter, 

 be'j-ins to make a small nest containing four or more cells in 

 which she lays eggs, and as fast as she builds additional cells, she 

 lays an egg in each. Presently, to these activities, is added the 

 fe'edino- of the larvae : one result being that the multiplication of 

 larvae involves a restriction of the food that can be given to each. 

 If we suppose that the mother-wasp rears no more larvae than she 

 can fully feed, there will result queens or mothers like herself, 

 relatively few in number. But if we suppose that, laying more 

 numerous eggs she produces more larvae than she can fully feed, 

 the result will be that when these have reached a certain stage 

 of growth, inadequate supply of food will be followed by pre- 

 mature retirement and transformation into pupae. What will be 

 the characters of the developed insects ? The first effect of 

 arrested nutrition will be smaller size. This we find. A second 

 effect will be defective development of parts that are latest formed 

 and least important for the survival of the individual. Hence we 

 may look for arrested development of the reproductive organs — 

 non-essential to individual life. And this expectation is in accord 

 with what we see in animal development at large ; for (passing 

 over entirely sexless individuals) we see that though the repro- 

 ductive organs may be marked out early in the course of develop- 

 ment, they are not made fit for action until after the structures 

 for carrying on individual life are nearly complete. The implica- 

 tion is, then, that an inadequately-fed and small larva will become 

 a sterile imago. Having noted this, let us pass to a remarkable 

 concomitant. In the course of -development, organs are formed 

 not alone in the order of their original succession, but partly in 

 , the order of importance and the share they have to take in adult 

 activities — a change of order called by Haeckel " heterochrony." 

 Hence the fact that we often see the maternal instinct precede 

 the sexual instinct. Every little girl with her doll shows us that 

 the one may become alive while the other remains dormant. In 

 the case of wasps, then, premature arrest of development may 

 result in incompleteness of the sexual traits, along with complete- 

 ness of the maternal traits. What happens ? Leave out the lay- 

 ing of eggs, and the energies of the mother-wasp are spent wholly 

 in building cells and feeding larvie, and the worker-wasp forth- 

 with begins to spend its life in building cells and feeding larvae. 

 Thus interpreting the facts, we have no occasion to assume any 



