294 MR. E. W. L. HOLT ON THE [Apr. 19, 



cockerel from a pullet by sight alone. I doubt whether a big male 

 Dragonet has the same power of discrimination with regard to his 

 own species. His demonstrations to young males or unripe 

 females are precisely similar to those which are directed to the 

 mature female, and the result is the same as in the case of 

 poultry — viz., the younger members flee in evident alarm. 



IV. Employment of the Secondary Sexual Characters for 

 purposes not connected with Reproduction. 



Dui-iug and after the breeding- season the males have been 

 observed to make use of their elongated dorsal fins for purposes 

 quite unconnected with sexual intercourse. I can neither aflirm 

 nor deny that their habits are the same at all seasons. After the 

 mullet had been removed from the tank it was first noticed by 

 Mr. Smith (and confirmed by frequent observations of my own) 

 that the mature males elevate their first dorsals in rushing at 

 worms {Nereis and Arenicola) dropped into the tank. When a 

 bunch of worms is dropped in, all the Dragonets, if not recently 

 fed, assemble to partake. The young ones are always the first on 

 the scene, but the advent of a large male, with dorsals extended, 

 is sufficient to scatter them. It is reasonable to suppose that the 

 display is intended to achieve this object. It is exhibited in- 

 differently by brilliant males and by those whose coloration has 

 decidedly faded. I do not think it unlikely that the fins are 

 displayed with this intent at all seasons ; the circumstances have 

 not at other times been so favourable for observation. 



Mature males when recently introduced into the aquarium do 

 not display the dorsals, except in the most momentary fashion, 

 when chased about the tank with a net; but when they have 

 remained in a tank for some days undisturbed, the approach of 

 the net is sufficient to ensure the dorsals being fully displayed, 

 and for a period more protracted than I ever observed during 

 courtship. Continued persecution causes momentary intensifi- 

 cation of the blue bands of the side, even when the yellow bands 

 have largely faded. The fish, in fact, continues to freely exhibit 

 his secondary characters until he succeeds in darting into a dark 

 corner or burying himself in the gravel. One can hardly hesitate 

 to believe that the fins are hoisted and the colours displayed with 

 a view to the intimidation of the intruder. There is a practical 

 difficulty in the way of testing the truth of this supposition by 

 the behaviour of the Dragonet in the presence of a predaceous 

 fish. To transfer either the one or the other to a strange tank is 

 not a fair test, and this must be borne in mind in considering the 

 conclusions to be drawn from the experiments which I have made. 



On the north side of the aquarium is a very large tank, the 

 further recesses of which are shrouded in obscurily. It is the 

 dwelling-place of sundry conger, dog-fish, skate, wrasses, &c., and, 

 in particular, of a number of large turbot, which last are in the 

 enjoyment of excellent appetites. On several occasions during 



