Gasterosteus aculeatus and G. spinachia. 243 



body had a peculiar, lateral, vibratile motion. They would fre- 

 quently seize hold of the nest and give it a violent tug, shaking 

 and tearing loose the vegetable matter of which it was composed ; 

 at other times they would carry to it, in their mouths, fine Con- 

 ferva-stems, and press them with considerable force into the walls 

 of the nest, or thrust them into the hole, which, by this means, 

 was sometimes partially concealed. Occasionally, each was ob- 

 served hovering over its nest, with the head close to the orifice, 

 the body being inclined upwards, at an angle of about 45°, fanning 

 it with the pectoral fins, aided by a lateral motion of the tail. This 

 curious manoeuvre was apparently for the purpose, so to speak, 

 of ventilating the spawn, which could be distinctly seen through 

 the orifice at the top ; at least, by this means, a current of water 

 was made to set in towards the nest, as was rendered perfectly 

 evident by the agitation of particles of matter attached to it. 

 This fanning or ventilating process was repeated, at short in- 

 tervals, during the day, and every day until the spawn was 

 hatched, to accomplish which took between two and three 

 weeks. 



Only one nest contained spawn ; the other was torn in pieces, 

 and the materials scattered about, in the hope that we might 

 have the pleasure of seeing it reconstructed. In this we were 

 not disappointed ; the fish immediately began to form a new 

 nest in exactly the same spot, and by the following day it was 

 more than half completed. It took a mouthful at a time, and 

 was at some pains in adjusting each load, spreading the mate- 

 rials out, and pressing them down with its mouth ; it then drew 

 its body slowly over the whole, vibrating, all the time, in the 

 same peculiar manner as when it forced its way through the 

 nest, as before stated*. 



On the 13th of June the hole at the top of the fruitful nest 

 was found to be much enlarged, so that the entire mass of 

 spawn was exposed to view ; and, on looking attentively, a few of 

 the newly hatched fry were seen flitting about the walls of the 

 nest. The assiduity of the parent was now greatly increased ; 

 it never left the spot ; by night it rested either on the nest or 

 by its side, and during day nothing was allowed to approach. 

 It fiercely seized a quill that was passed down towards the ob- 

 ject of its solicitude, with such vigour that the shock of attack 

 was distinctly felt by the hand. Combats with its companions 

 became more frequent ; but its ire was chiefiy directed against 

 its neighbour, which, like itself, was engaged in parental duties. 

 This having also a nest to defend never shrank from the confiict, 



* It is probable that it is the male fish which builds and guards the 

 nest ; and, if so, it might, perhaps, be shedding the milt when dragging its 

 body over and through the nest in the manner described. 



16* 



