ioo NATURES STORY OF THE YEAR 



herself along, so that the tail at one side, and 

 possibly the head at the other, are all that is 

 visible of her. 



The male now seems to go mad. He stares for 

 a moment at the nest and its occupant, then rushes 

 around the spot, returns and stares again, as 

 though unable to believe the evidence of his eyes. 

 And woe betides any fish venturing to make an 

 attack at this time. After a minute or two the 

 female, having laid her eggs, quits the nest, and is 

 immediately attacked and chased away by the 

 male, who seems to have forgotten his former 

 manner towards her. 



The nest is so dense that water cannot easily 

 flow through it. But fresh water must constantly 

 pass to the eggs or they will die. So the male 

 frequently fans them with his pectoral fins, mean- 

 while using the tail to maintain his position over 

 the nest. Thus two currents are produced, the 

 one passing forward from the fish into the nest, the 

 other backward from the tail. This curious con- 

 trary motion of fins and tail never occurs except 

 on the occasion and for the purpose indicated. 

 It is apparently peculiar to the male stickleback. 



