FISHES’ EGGS 17 
have commenced to swim about, they return to the 
parental pouch when alarmed. And strangest of all is 
the arius, a fish found in Ceylon and Guiana, which 
protects its eggs by carrying them in its mouth. 
There appear to be only one or two cases in which 
the female alone takes charge of the eggs. One is a 
fish (Aspredo batrachus) about a foot in length found in 
tropical Africa. The skin on the lower part of this 
fish’s flattened body becomes soft and spongy, and 
when the eggs are laid she presses them into the 
spongy skin by lying on the top of them, and carries 
them about with her in this way until the young are 
hatched. As soon as this has occurred, the skin on 
the under-surface of her body becomes as smooth as 
before. 
A parallel to this we find amongst amphibians in 
the toad known as the pipa, except that in the tonrd it is 
the skin of the back that becomes spongy. Both the 
male and female butter fish take their share in guarding 
their eggs by rolling the eggs up into a ball, and each 
in turn wrapping his or her Jong body round the mass. 
The number of eggs deposited by any particular fish 
is directly in proportion to the protection they receive 
and to the likelihood of their being fertilised. The ling 
merely sheds her eggs into the sea, and produces over 
half a million eggs to each pound weight of her body. 
The trout deposits about a thousand eggs to each 
pound weight of her body, for these are partially pro- 
tected by being buried in the gravel. The stickleback, 
c 
