Instinctive Behaviour of Fishes 1 1 1 



is another nest-building bony fish. During the 

 spawning season the male assumes a metallic 

 green hue, the lower part of his throat being a 

 bright crimson colour. The fish constructs his 

 nest in the water it inhabits by collecting a 

 quantity of grass-stalks, which he cements 

 together with a layer of mucus exuded from 

 the surface of his body. In this way a dome- 

 like hollow structure is reared in the side of 

 which a hole is left, its edges being strengthened 

 and rounded off with great care. The fish then 

 seeks a mate, and conducts her to the nest he 

 has made; she enters it, and in a few minutes 

 has laid some eggs. This process is repeated 

 day by day until the nest contains a consider- 

 able number of eggs. The male then takes up 

 a position for a period of about a month to 

 defend the nest from invaders. During this time 

 he has frequently to fight with larger fish than 

 himself; in making these attacks the little 

 creature seizes their fins and strikes furiously 

 at their head and eyes. As the young fish 

 appear and grow they are apt to stray ; the male 

 brings them back to their allotted precincts 

 until such time as they are able to protect them- 



