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. 
Figure, shewing the ventral fin. 
