414 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1921. 



I iceship in their trades. Therefore, in the egg something is registered 



on the substance of the future nervous tissue that, at a certain period 

 in the future caterpillar's life, gives the command to work, to spin 

 and weave a house of silk. Then, on this same or other nerve tissue, 

 another command is registered, to be effective only after the other 

 has been executed, which says, " cease work and take life easy." A 

 third says, " travel." A fourth in turn says, " find some secluded 

 place, regardless of the nature of the surroundings, and there sur- 

 round yourself completely with a case of silk." After this the purely 

 vegetative forces become predominant and changes follow in which 

 regulated movements have no part, The change to the pupal stage 

 and the final transformation to the moth are all physiological proc- 

 esses of growth ; but even here the shedding by the pupa of the larval 

 skin and the escape from the cocoon by the moth are acts of coordi- 

 nated instinct. The moths themselves are bound by few rules of 

 conduct. When the instincts to mate and to lay eggs on the leaves of 

 trees have been fulfilled, their duties and their lives are ended. 



Though we may have no unquestioned evidence that the power of 

 reason is possessed by any insect, still, can we conceive that a mere 

 mass of organized matter can do all the things that a webworm does, 

 and yet have nothing in common with ourselves? Can the cater- 

 pillars have appetites, a sense of touch, fear of danger, and show 

 resentment at an interference with their natural rights without some 

 consciousness at least of their own existence? Does the worm turn 

 with no more emotion than a piece of rubber? And, can we really 

 believe it even if we think so? 



Fig. 12. — Moths of the fall webworm, a pure white and a spotted individual (a little 



larger than natural size). 



