476 D. W. CUTLER. 
Miss Esdaile from her examination of salmon scales found that those 
taken from various regions of the body invariably show great changes 
in the number of the sclerites formed. This undoubtedly occurs in the 
Plaice and Flounder, but by no means to the same extent ; when it is 
found there is a correlation between the number of sclerites and the 
size of the scale, the longest scale having the greatest number of sclerites. 
Winge found that in the cod there were considerable variations in the 
breadths of corresponding sclerites of different scales. I have not had 
the same experience in either Plaice or Flounder scales. It is obvious, 
therefore, that the growth of a big scale does not consist in making 
broad sclerites, but in increasing the number. 
The scales from fishes of different ages have been examined, and in 
all cases I have found that the growth rings which they exhibit are identi- 
cal with those which were seen on the otoliths. Scale curves exhibiting 
these rings are given in Figs. 2, 3 and 4. Fig. 2 shows curves from five 
first year fish : six curves from two and three year old fish respectively 
are seen in Hig. 3: while Fig. 4 represents six curves from three four 
and three five year old fish respectively. 
It will be noted that the periods of maximum and minimum breadth 
formation in the sclerites are very clearly shown. 
It will also be seen that the first sclerite of the scale, that is the one 
nearest to the centre is always broad, the succeeding ones becoming 
narrower as the distance from the centre increases. This is of interest 
in connection with the view that I hold, that the width of the scale 
primarily depends on the temperature of the surrounding water. The 
young of the Plaice and Flounder are usually born about the end of 
April: scales are, however, not produced until a month or six weeks 
later, thus the scale growth is not begun until the temperature of the 
water is relatively high. At this period the temperature of the sea at 
Plymouth is usually between 13° and 13°5° C., as compared with about 
9° C. in March. The same fact was noted by Winge for the cod scales 
which he examined from the Faroes. 
Although the maxima and minima of the curves are quite sharply 
marked out, yet in many scales one notes minor depressions or elevations 
as in the scales D Fig. 4 or H Fig. 3. These secondary maxima and 
minima, as they have been called by Winge, are very common and are 
due, I think, to local variations of the conditions in which the animal 
was living. A short period of lowered temperature being sufficient to 
account for a secondary minimum: the converse conditions bringing 
about a secondary maximum. 
In Table I. (p. 491) I have given the details of some of the fish which 
I have examined. The first column gives the age as determined by the 
otolith, the second the length as measured from the tip of the snout to the 
