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 toad 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 long body round the mass. 



The number of eggs deposited by any particular fish 

 L cHrectly 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 





