184 The Field Naturalist'' s Quarterly Aug. 



" smolt " of 6 or 7 inches long may be two years old or there- 

 abouts, and the "grilse," which is the salmon on its first 

 return from the sea, will be some six months older. The 

 age of full-grown older salmon is more difficult to determine, 

 and we have to fall back on comparisons of size. Weight is 

 in all cases deceptive, for so much depends on recent feeding 

 and on general opportunities of nourishment. 



Coming to the sex of fishes, we find somewhat more satis- 

 factory evidence to go upon. Here, too, comparisons of size 

 are not quite unimportant ; for it is found that in teleosteans, 

 or bony fishes, at any rate, the female is the larger for her age, 

 though there are exceptions in plenty, such as, for instance, 

 Callionymus and Arnoglossus. Size as an indication of sex is 

 most apparent in the conger eel, for every individual 

 measuring upwards of 2 feet 6 inches may safely be re- 

 garded as a female. The female conger also has a more 

 pointed snout, while that of the male is blunt. Similar 

 distinctions in the shape of the snout are noticeable in the 

 fresh-water eel. The external sexual characters of fishes are, 

 with the exception of the claspers in sharks and rays and the 

 pouch in pipe-fishes, practically all of the "secondary" kind 

 — that is to say, they have no connection with the function 

 of reproduction. Size, colour, and seasonal developments in 

 the fins are among the commonest secondary sexual charac- 

 ters in the fish world. The most striking case of difference 

 in colouration of the two sexes is that of the dragonet 

 {Callionymus), the brightly coloured male of which differs 

 in so marked a degree from the duller female that they were 

 long known by different names, the former being called the 

 Gemmeous Dragonet, while his mate went by the title of 

 Dusky Skulpin. This and some other fishes, such as the 

 lumpsucker (the sexes of which are known in Scotland as 

 the cock-paidle and hen-paidle), remind the naturalist of the 

 sex differences in the plumage of birds, and indeed the differ- 

 ence between the male and female dragonet is not less than 

 that between the black cock and grey hen or between the 

 cock and hen pheasant. In fact, the sex distinctions in the 

 dragonet do not end with mere colour, for the male has a 

 larger head than the female, and he may further be recognised 

 by the long filaments that develop in the dorsal fin. In the 



