AS AN INDEX OF AGE. 57 



That ill the life of fish, as in trees, there will be good years and bad 

 years is more than probable, and as this variation in metabolism 

 expresses itself in the stems of trees, one might, reasoning from analogy, 

 expect a similar change in the scales of fishes. That such an effect does 

 take place appears probable from my figures and photomicrographs. 



In regard to locality of capture, as my work was mainly done at 

 Plymouth, most of the fish examined were from the western portion of 

 the English Channel, chiefly from the bays of Devon and Cornwall. 

 Few of the fish examined were captured by the ocean-going trawlers, 

 as in fish caught hj this method the scales were, as a rule, completely 

 rubbed off by the time the fish came to hand. 



If, as in the case of a few whiting, etc., the fish examined were 

 captured at other localities, I have stated that such is the case in the 

 column of notes. 



The haddocks examined were caught in the North Sea, off the Firth 

 of Forth, in Aberdeen Bay, and off the Shetlands. 



The cod, only a very few statistics about which I am able to give, 

 were brought in at St. Andrews. 



A friendly critic has suggested that annual rings would either not be 

 found, or would not be clearly marked, in scales from fish of deep water, 

 on account of the fact that in this case fish are not exposed to the same 

 seasonal variation in temperature as in shallow water; in other words, is 

 it not probable that the growth of fish living in deep water will be less 

 accelerated in the summer and less arrested in the winter than in forms 

 living in shallow water. In order to determine if such was the case, I 

 compared scales from a series of haddock (10-15 inches in length) 

 captured in comparatively shallow water (8-14 fathoms) at Aberdeen 

 Bay with another series (10-16 inches) caught in deep water (60-80 

 fathoms) seven miles off the Shetlands. The result of my observa- 

 tions was that annual rings were as clearly marked in the scales of 

 haddocks from deep water off the Shetlands as in those from shallow 

 water of Aberdeen Bay, excepting that in the older stages of the former 

 the rings appeared very slightly less clearly defined. 



The weights of fish in the statistical tables must be slightly allowed for 

 as not being exactly accurate, as in most cases the fish were weighed 

 after having been for some time in spirit or formalin. 



THE OCCURRENCE OF MINUTE SCALES. 



In my observations on the skin of Gadidse I noticed the presence of 

 minute scales situated near the larger and better developed. These 

 minute scales I found chiefly in the younger stages of the fish. In older 

 stages of the animal tliey appeared to be almost entirely covered over 

 by the larger ones, and to lie in such positions that their growth would 



