182 FIFTEEN-SPINED STICKLEBACK. 



and if the guardian is forced to retreat by the receding of 

 the tide, he returns as soon as the way is open, and for three 

 or four weeks he continues his guard, until the young are 

 able of themselves to take their chance in the broad expanse 

 of sea. So much is he intent on the principal object of his 

 solicitude, that at this time himself may be easily caught; but 

 he resents every interference with the nest; and if the grains 

 of ova be exposed to sight, as was done by way of trial, the 

 breach was immediately repaired by the labour of dragging 

 the materials into a position by which they are again concealed 

 and protected. 



A singular instance of constructive skill and patience in the 

 formation of its nest, which occurred within my knowledge, is 

 deserving of remembrance. The situation selected was the 

 loose end of a rope, from which the separated strands hung 

 at about a yard from the surface, over a depth of four or 

 five fathoms; and to which the materials could only have been 

 brought, of course in the mouth of the fish, from the distance 

 of about thirty feet. They were formed of the usual aggregation 

 of the finer sorts of green and red ore- weed; but they were 

 so matted together in the hollow formed by the untwisted 

 strands of the rope, that the mass constituted an oblong ball 

 of nearly the size of the fist; in which had been deposited 

 the scattered assemblages of spawn, and which was bound into 

 shape with the thread of animal substance already described, and 

 which was passed through and through in various directions, 

 while the rope itself formed an outside covering to the whole. 

 We can scarcely suppose that such a nest can have been the 

 work of more than a couple of fishes, but the grains of 

 spawn had grown to almost the size of radish seeds, and in 

 collective bulk seemed greatly disproportionate to the size of 

 the parent, and only to be explained by the well-known fact, 

 that the ova of fishes generally obtain an increase of bulk by 

 the absorption of water after exclusion; which fluid may be 

 supposed to exert considerable influence on the further de- 

 velopment of the young. The embryo of this fish, as is 

 believed to be the case with many others, is not found to 

 bear a close resemblance to the parent, and, in fact, may be 

 said to pass through a decided metamorphosis in the course 

 of its final development. 



