192 THE ZOOLOGIST. 



the fish with beef to come out, in order that I might watch the 

 course it took in returning home. What is the explanation of 

 this curious behaviour in following a certain course and then 

 changing it and darting suddenly home ? Is it merely an idio- 

 syncrasy of this fish, or a characteristic habit of Eocklings in 

 general? Is it, as I am inclined to believe, an instinctive 

 attempt of the Kockling to mislead possible enemies as to the 

 real position of its resting-place ? It will be observed, on looking 

 at the plan, that in the region of E the dark slate at the back 

 of the aquarium is not covered with rockwork (though it is 

 covered above the level at which the plan is supposed to be 

 taken). I thought at first that perhaps this nocturnal fish, 

 when it had secured some food, instinctively directed its retreat 

 towards the dark patch, and this idea may have already occurred 

 to the mind of the reader. But this apparent explanation is 

 shown to be wrong, when it is remarked that the aquarium is in 

 a dark place (lighted when necessary by an electric lamp from 

 above), and that the corners or P would have been as likely 

 to attract such a poor- sighted fish as the Eockling. Again, why 

 should its speed be greater when it was making the turn from 

 E or J than at other times, or why did it not creep round the 

 rock A to reach B, as one would have expected it to do, instead 

 of passing across the open water between D and E ? 



On March 23rd (i. e. about sixteen weeks after introduction 

 of the Eockling) I put several Common Gobies into the aquarium. 

 The largest Goby was about three and a half inches in length, 

 or about half the length of the Eockling. Immediately the 

 Gobies were dropped into the water they darted away into holes 

 and crevices in the rocks, and when one of them dashed into the 

 place where the Eockling lay, the latter seemed so much alarmed 

 that it at once quitted its hiding-place and took up a position 

 (shown in dotted outline at M) at the foot of the vertical rock N 

 at the back of the tank, with its tail slightly curved, and its 

 head directed towards the right and looking somewhat towards 

 its old hiding-place. In this position, or nearly in this position, in 

 which it is much exposed to view and to the attacks of enemies, 

 if there were any in the tank, it remained, lying almost motion- 

 less, at least in the daytime, up to May 1st. If it moved at all in 

 the daytime, it was only for an inch or so towards the right and 



