172 SALT-WATER FISHES 



Stage by stage with the helpless newly hatched larva of any 

 egg-laying fish. 



Mcintosh, who had opportunities of studying these young 

 viviparous blennies in a tank reserved for their sole use, found 

 them under these conditions stretching themselves along the 

 horizontal branches of zoophytes, and feeding on the hydroid 

 polyps and tiny sessile-eyed crustaceans that they found in such 

 situations. The upward turn of the eyes is, as in the weever 

 and some other star-gazing forms, less noticeable in the larval 

 stage than in the adult. 



Cunningham draws attention to the fact of both this and 

 our other viviparous bony fish, the bergylt (Sehastes\ being 

 of northern origin. There is some doubt whether this blenny 

 can have more than one family in the year. 



Gasterosteidae 



The Fifteen-Spined Stickleback 



Three British sticklebacks, with a bewildering series of 

 varieties and races, are commonly described ; but, although 

 two of these seem equally at home in the head-waters of 

 rivers and their brackish estuaries, one only need be seriously 

 regarded as a sea fish. 



The Fifteen-spined Stickleback {Gasterosteus spinachia) is 

 recognisable by its tubular pointed mouth, its scaleless, bony- 

 plated body (both more or less characteristic of the next 

 group), and its fifteen short spines along the back. In colour 

 it is greenish brown, with variable lines and spots. It is said 

 to change its colour at will when excited, but there seems 

 to be little circumstantial record of this phenomenon. Nor 

 has the male been described as changing his hue in the 

 breeding-season, though in our two fresh-water species the 

 males become bright red when guarding their nest. 



The sticklebacks have, in fact, among fishes, much the 

 same interest for naturalists as the nightjar among birds. That 



