236 
HAROLD’S DISCUSSIONS. 
cent females and forty-tliree per cent males. Young 
fed some on beef, and seventj-eiglit per cent devel¬ 
oped into females; others lie fed on fish, obtaining 
eighty per cent females; and of those that he fed on 
frogs, ninety-two per cent became females. He 
found that tadpoles pass through a stage when they 
are both male and female, and he claims that their 
food during this period has an effect on their sex. 
A naturalist in 1870 took a number of pupse of 
the Saturnia moth from Texas to Switzerland. These 
turned into moths like their ancestors, but their larvae, 
feeding on the leaves of entirely new plants, meta¬ 
morphosed into moths so unlike their grandparents 
that they are recognized as a different species. 
In Ruatan I saw a parrot which was green all but a 
spot on the head. For some time it had access to salt 
pork, and ate some every day. Its feathers turned 
yellow, excepting the spot on the head, which remained 
red. I have also heard that a yellow canary fed on 
cayenne becomes orange - colored, and a bullfinch 
which is given hemp-seed will change its color to 
black. 
Mr. John Hunter fed gull, which is a fiesh-eat- 
ing bird, on grain for a year, and he found that 
during that period the soft lining of the stomach had 
so changed and hardened that it resembled that of a 
chicken, a grain-eater. According to Edmonstone, 
this same operation is repeated in nature without 
man’s help. He observed that another species of gull 
in the Shetland Islands changes its stomach to a great 
extent twice a year. Half the year its diet consists 
