PHYSIOGENESIS. 



235 



colored. It then seemed possible, althougK highly im- 

 probable, that the varnish itself might act as a stimulus 

 similar to that caused by gilt or white surroundings, 

 and therefore the experiments were repeated with black 

 surroundings in darkness, but the pupae of the two sets 

 were again almost identical, so that it appeared cer- 

 tain that the eyes can have nothing to do with the in- 

 fluence. 



" It then seemed possible that the large branching 

 bristles, with which the larvae are covered, might con- 

 tain some organ which was affected by surrounding 

 colors, but experiments in which half of the larvae were 

 deprived of their bristles showed conclusively that the 

 sensitive organs must have some other position, for 

 the pupae from both sets of larvae were identical. 



" I was thus driven to the conclusion that the gen- 

 eral surface of the skin of the caterpillar is sensitive to 

 color during stage ii, and part of stage iii. In order 

 to test this conclusion, I wished to subject the body of 

 the same larvae to two conflicting colors, such as black 

 and gold, producing the most opposite effects upon 

 the pupa. Such an experiment, if successfully carried 

 out, would decide some important points. If the part 

 of the body containing the head was not more sensi- 

 tive than the other part, a valuable confirmation of the 

 blinding experiments would be afforded. Mrs. Bar- 

 ber's suggestion that particolored pupae may be pro- 

 duced by the influence of two colors would be tested 

 in a very complete manner ; if particolored pupae were 

 obtained, it seemed probable that the light acts di- 

 rectly upon the skin, but if they could not be obtained, 

 it seemed more probable that the light influences the 

 termination of nerves in the skin, and that the pupal 

 colors are produced through the medium of the nervous 



