FISHES AND SEA-SQUIRTS. 309 



the tapering posterior end of the body. The tails of the 

 three forms are indeed worth careful comparison, for in the 

 shanny the tail fin is distinctly separated from the anal and 

 dorsal, in the gunnel these meet it, but the tail fin persists 

 unaltered ; a similar arrangement obtains in the young vivi- 

 parous blenny, but as it grows older the tail fin disappears, 

 leaving only the united dorsal and anal. In general shape 

 the viviparous blenny may almost be said to be intermediate 

 between the shanny and the gunnel, for it is less elongated 

 and compressed than the latter, and more so than the former. 

 The long dorsal fin, instead of having a notch as in the 

 shanny, has near the tail a region containing ten spines, 

 whose height is considerably less than that of the soft rays 

 which support the rest of the fin. The result is to produce 

 what is known as a "depressed" region in the fin, a very 

 characteristic peculiarity. The anal fin is longer than in 

 the gunnel, for it extends through about three-fifths of the 

 body-length. 



After the blennies we come to that most interesting 

 family, the sticklebacks, which are more or less familiar 

 to most people. In rock pools the commonest form is the 

 fifteen-spined stickleback (Gasterosteus spinachia), which 

 reaches a length of six or seven inches. In spring and 

 early summer the pools often swarm with the young, which 

 are most charming little creatures, and hardy in confinement, 

 while a lucky naturalist may now and again find the nests, 

 with the fierce father watching over the precious contents. 

 The nests are, however, most usually in spots sheltered from 

 violent wave-action. 



There is no difficulty in recognising a specimen of the 

 fifteen-spined stickleback, for the long snout and small 

 mouth, the fifteen spines which represent the first dorsal 

 fin, the row of strong plates at each side of the body, and 

 the expanded fan-like anal, second dorsal and caudal fins, 

 are all eminently characteristic structures. There is also 

 something so peculiar about the way in which the little fish 

 roots about with its long snout, and directs its tapering 

 body in and out of the rock crevices, that one recognises it 

 at once as different from the bullheads or blennies the 

 other common rock fishes. Like the other sticklebacks, it 

 is an active and pugnacious little fish, though its habits 



