VARIATION BY ENVIRONMENT. 
243 
They became larger, and changed their color to yel¬ 
low in the second generation. 
The horses of Normandy are large, while those of 
Brittany have always been small. Norman horses 
were sent to Brittany and at once began to degen¬ 
erate, so that in the third generation they were like 
the native horses. Normandy is remarkable for its 
moist climate and lush vegetation. 
On the smallest of the Madeira islands everything 
is diminutive—people, horses, cattle, and even the 
smaller animals. The Yanessa butterfly presents an 
interesting phase of life. There are two species, the 
levana and prorsa. The levana is hatched in the 
spring; it is red, with black and blue spots. It lays 
eggs which are hatched in the summer as the prorsa^ 
which is deep black, with a yellow band on the wings. 
The prorsa lays eggs which again produce levana but¬ 
terflies the next spring. Levana eggs have been put in 
a refrigerator in the summer. They came out butter¬ 
flies, having the characteristics of both the levana and 
the prorsa. The warm weather has clearly the effect 
of changing the color of an insect to a great extent. 
It is well known that the ringed snake lays its 
eggs in the sand and leaves them for the sun to hatch. 
When the snake is put into a box where there is no 
sand it brings forth its young alive. 
The whale is an illustration of a singular change. 
From fossils it is clear that it lived mostly on land 
during the Mammalian age in a manner much like that 
of the beaver. Instead of developing and adapting 
its body to more perfect land existence, it chose the 
