PH YSIOGENESIS. 23 1 



had been found on tarred fences and in subdued light ; 

 light ones on light surfaces ; while green leaves were 

 shown to produce green chrysalides, at any rate in cer- 

 tain cases. 



"During the following nineteen years, gradual con- 

 firmation of Mr. Wood's central position was afforded. 

 In 1873 Professor Meldola supported the observations 

 upon the chrysalides of the "garden whites. " He 

 compared large numbers of individuals and found that 

 the pupae upon black fences were darker than those 

 upon walls. 



"In 1874 a paper by Mrs. M. E. Barber, and com- 

 municated by Mr. Darwin to the Entomological So- 

 ciety of London, was printed in the transactions of 

 that society. Mrs. Barber had experimented with a 

 common South African swallow-tailed butterfly (Papi- 

 lla nireus*), and had found the chrysalis wonderfully 

 sensitive to the colors of its environment. When the 

 pupae were attached among the deep green leaves of 

 the food-plant, orange, they were of a similar color ; 

 when fixed to dead branches covered with withered, 

 pale, yellowish-green leaves, they resembled the latter. 

 One of the caterpillars affixed itself to the wood frame 

 of the case, and then became a yellowish pupa of the 

 same color as the wooden frame. 



"Mr. Maurel Weale also showed that the color of 

 certain other South African pupae can be modified, and 

 Mr. Roland Trimen made some experiments upon an- 

 other African swallow-tail (Papilio demoleus} confirm- 

 atory of Mrs. Barber's observations. He covered the 

 sides of the cage with bands of many colors, and found 

 that green, yellow, and reddish-brown tints were re- 

 sembled by the pupae, while black made them rather 

 darker. Bright red and blue had no effect. The larvae 



