Nest-Building Fishes. 165 



nuptial lustre, shows remarkable activity in selecting a site 

 for an edifice, and transporting the building material thither. 

 Fragments of all kinds of plants, gathered often at a distance, 

 are brought home in his mouth. These are arranged as a 

 sort of a carpet, but as there is danger of the light materials 

 being carried away by the current, they are weighted down 

 by sand to keep them in their places. Having entwined them 

 with his mouth to his complete satisfaction, he then glides 

 gently over them on his belly, and glues them with the 

 mucus that exudes from his pores. More solid materials, 

 sometimes bits of wood, sometimes bits of straw, which he 

 seizes with his mouth, are adjusted to the sides of the floor 

 to constitute the walls. He is now very particular. If the 

 piece cannot be properly adjusted to his building, and he 

 does not lose patience in his efforts to fit it in, he carries it 

 to some distance from the nest and leaves it. After the side 

 walls are erected, a roof of the same materials with the floor 

 is laid over the chamber. Firmness is given to the whole 

 structure by passing over it with his body, the light and 

 useless particles being fanned away by the action of his fins 

 and the vibratory movements of his tail. In carrying on his 

 building operations care is taken to preserve a circular 

 opening into the chamber, his head and a great part of his 

 body being thrust therein, thus widening and consolidating 

 it, and rendering it a fit receptacle for the, female. When 

 choosing material, the fish has been seen testing its specific 

 gravity by letting it sink once or twice in the water, and if 

 the descent was not rapid enough finally abandoning it. 



Of the exact method used by the fish in binding the nest 

 together we are indebted to Prof. Ryder. The male fish 

 spins from a pore or pores a compound thread, using his 

 body to insinuate himself through the interstices through 

 which he carries the thread. The thread is spun fitfully, 

 not continuously. He will go round and round the nest per- 

 haps a dozen times, when he will rest awhile and begin anew. 

 Its shape is somewhat conical before completion. The 



