218 DEVELOPMENT AND HEREDITY. 



and earlier in successive generations, i.e. tend to be 

 transferred from the end of development back toward 

 the beginning. But in the butterfly the backward 

 transference is limited by the slow and variable de- 

 velopment of the caterpillar stage. The changes of 

 development are therefore compressed and heaped 

 up, in the period during which each generation lies 

 quietly protected in the shelter it has made for itself. 

 Thus the greater part of its development may take 

 place in the chrysalis stage. 



By following this line of supposition, we can see 

 how forms might arise in which, the larval life being 

 greatly prolonged, and the chrysalis life being abbre- 

 viated, the stored nutrition or potential energy of 

 the larva might suffice not only for the chrysalis 

 stage, but also for the adult stage, so that the mature 

 forms might reproduce before they had ever partaken 

 of food. The result would be that, in the course of 

 generations, the habit of taking food would be lost 

 bv the mature form, especially if the supply of food 

 for the mature forms failed. When the habit of 

 eating were lost, the corresponding organs would 

 degenerate and disappear by reason of disuse. But 

 since it is necessary for an organism to attain matu- 

 rity in order to reproduce, the mature state, however 

 brief, must be its final stage of development so long 

 as the species exists, — even though it be in the 



