PURPLE-FINNED SAILOR-FISH. Hislioplumus immaaildtus. 



and it is a curious fact, that it gradually decreases as the fish approaches to maturity ; 

 whereas in the seas around Ceylon, it retains its full size throughout the entire period of 

 life. They raise it above the water whilst dashing along the surface in their rapid course, 

 and there is no reason to doubt that it occasionally acts as a sail." 



In this genus the ventral fins are reduced to one, two, or three spines, which in the 

 present species are two in number. The tail is very deeply forked, and the enormous 

 dorsal fin is a uniform deep blue. 



WE now arrive at the large family of the Gobies, which include many curious fish, and 

 of which the British coasts present many representatives. 



The BLACK GOBY, sometimes known as the BOCK-FISH, is a moderately common 

 example of the enormous genus to which it belongs, and which contains more than a 

 hundred and fifty authenticated species. The members of this genus may easily be 

 recognised by the peculiar form of the ventral fins, which are united together so as to form 

 a hollow disc, by which they can attach themselves to rocks or stones at pleasure. In 

 fact, this disc, although differing in shape, acts on exactly the same principle as that of 

 the sucking-fish. 



The Black Goby prefers the rocky to the sandy coasts, and may be found in the pools 

 left by the retreating tide. Some naturalists deny that the disc is used for adhesion, but 

 I have caught and kept many Gobies, and have frequently seen them sticking to the sides 

 of the vessel in which they were confined. The adhesion was achieved with astonishing 

 rapidity, and the little fish contrived to hold itself with wonderful tenacity. The surface 

 of the Black Goby is very slippery, owing to the abundant mucous secretion which is 



