REPRODUCTION AND HEREDITY 



277 



opinion. In April or May the male stickleback builds out of 

 fibres a little tube-like nest, sometimes supported by, and hidden 

 between, the stems of water plants, but more frequently, for the 

 sake of greater security, buried deeply in the sand at the bottom 

 so that only one opening is visible. Marital faithfulness exists 

 neither in male nor female ; numerous females are fertilized and 

 compelled to lay a few eggs, until at last several hundred eggs 



FIG. 67. Geophagus brachyurus. MALE WITH YOUNG. 



have been collected. While the work of the female ceases with 

 the egg-laying, for the male begins now a period of much 

 sacrifice and hard work. Untiringly he keeps guard over the 

 safety of the nest and the well-being of the growing young. 

 Frequently the male stands for hours over the entrance to the 

 nest, and by gently moving his pectoral fins fans towards the 

 young a continuous stream of fresh water rich in oxygen. The 

 courage of this little fearless fish is astounding, and even larger 



