THE METAMORPHOSES OF THE NERVOUS SYSTEM. 



41 



least and the most tardily. The butterfly, once escaped from 

 its chrysalis case, is found to have undergone extraordinary 

 alterations in the nervous system. The abdominal ' chain of 

 ganglions appears to be formed of four masses only ; the nervous 

 centres of the first two segments of the abdomen of the caterpillar 

 state have disappeared by uniting with the enlargement in the 

 metathorax ; and those of the last four rings have become 

 concentrated into one mass. 



Newport has given us th^ results of his study of the progressive 



LARVA AND PUP^ OF Var.e:sa lo. 



The larva just suspended ; three stages of chrysahs development ; the larva-skin gradually 



separating. 



changes in the nervous system of the small tortoiseshell butterfly 

 {Vanessa urticci), and his history of the structural alterations 

 that take place hour after hour is certainly most remarkable. 

 This butterfly undergoes its changes in fourteen days, and the 

 caterpillar suspends itself to undergo its transformation into the 

 pupa or chrysalis. " Two hours," writes this excellent observer, 

 " after the larva of Vanessa urticcB has suspended itself to undergo 

 its transformation, and in which state it remains from six, eight, 

 ten, or even twenty-four hours — according to the strength of 

 the individual and other circumstances — before it throws off its 

 last larva skin, a considerable alteration has already taken place 

 in the body of the larva. The ganglions in the head are still 



