vii ASSIMILATION AND READJUSTMENT 137 



when the enemy is out of sight. In B rerun's nierleben 1 

 there is a terrible account showing " furens quid femina 

 possit" even among fish. Rival female Paradise fishes 

 had to be separated by a glass partition. This would not 

 prevent them from futile attempts to injure each other, 

 and when a curtain was hung over the glass to hide the 

 hated rival charms from the sight of each, they glutted 

 their morbid feelings by getting round it so as to stare at 

 each other. Finally, one jumped clean over the partition 

 to resume the attack. Out of sight, it will be seen, is not 

 altogether out of mind among fish. The hereditary 

 tendencies to envy, hatred, malice, and all uncharitableness 

 are definitely concentrated upon a certain object. It is 

 not merely the sight of that object that will arouse the 

 instinct. There is a state of permanent excitation or 

 excitability of which the object is the centre, and under 

 stress of which the hostile action may be continued or 

 renewed just as though the enemy were still in sight. Ot 

 the difference between this permanence of excitability, 

 with its renewed discharges of nervous energy and true 

 recognition, a beautiful example is drawn from the obser- 

 vations of sticklebacks by Evers. 2 Sticklebacks found 

 with their nests and transported into a tank neglected 

 them the moving disturbed the habitual course of action. 

 But sticklebacks that had built in a tank would take care 

 of eggs collected in the open like their own. The sight of 

 the egg in the nest is enough to excite the parental 

 tendency. But what is most significant for our purpose 

 is the case of one stickleback in particular, which was 

 taken from his nest to another tank. The nest was put in 

 after him, and both he and his nest were attacked by 

 several females, so that it became necessary to cover the 

 nest with sand. After swimming about wildly for a time 

 he began to recover, and appeared to be searching, and 

 Evers, by way of helping him, brought some of the eggs 

 to the surface as he approached. Some of the females 



1 ib. Vol. VIII. pp. 187, 1 88. 



2 Brehm, VIII. pp. 171, 172. Evers justly remarks that it is impos- 

 sible to decide whether he recognised the nest as his own or not. Com- 

 parison with the other cases mentioned suggests the explanation offered 

 in the text. 



