156 



ROCK GOBY. 



the second dorsal and anal fins; and it is to be observed, as 

 a general rule applicable to all fishes, that although the scales 

 increase in size with the growth of individuals, they are not 

 known to vary in number with difference of age." Professor 

 Nilsson says that in the female the pectoral and ventral fins are 

 shorter than in the male, and the two dorsals further apart. 



Figxire, shewing the ventral fin. 



