ANNUAL RINGS IN SCALES. 487 
was as regards the amount of food given to them. As the experiment in 
the case of these two classes of animals progressed satisfactorily from the 
very beginning, that is from July, 1915, until October, 1916, I have 
included scale curves in the figures for the period, July, 1915, to January, 
1916. 
As regards the sclerites the Tables V and VI shows a uniformity 
among the fishes of the abundant tank which were in good condition ; of 
those in a bad condition at the end of the experiment I shall treat later. 
Figs. 8 and 9 (p. 481) are scale curves of abundant and scanty fed 
fish respectively. They are very alike in their general aspect as regards 
the type of curve, and in each set the maxima and minima are produced 
at approximately the same time and in accordance with the rise or fall 
of temperature at that time. Further it will be noted that there is 
correspondence between the course of these curves and those of the 
control fish scales of the same period. 
If food were the predominating cause of the winter and summer rings 
of the scales, the expectation would be that the scales from the two sets 
of fish would have been remarkably different : this, however, we see is 
not the case. 
The increase in length of the fish, as shown in the table, is very 
different, the scantily fed animals not increasing to any great extent. 
Also the number of sclerites produced by the abundantly fed fish is in 
excess of those produced by the animals in any of the other tanks. 
Figs. 8 and 9 show very clearly the great difference between the num- 
ber of sclerites produced for a given period by fish in the two tanks. 
The last scale figured, No. 13 of Fig. 8, is interesting in this connexion : 
the condition of the animal was never very good, and at the end of the 
experiment the increase in length was only 1 cm. ; that is, for a period 
of nine months this animal had only added lem. to its length. In 
accordance with this we note that but 13 new sclerites had been added 
to the scale ; thus though the animal had been given the opportunity 
for feeding well it had for some reason not availed itself of it, and had 
thus become comparable with the fish of the scanty tank. 
The converse of this occurred once or twice with the scantily fed fish, 
in that some of the more vigorous animals managed to obtain more 
than their share of the food given to them; with the result that they 
increased in length much more than did their fellows and developed many 
more sclerites. Most examples of this have been omitted from the table, 
but scale No. 14 for the period of May to October exhibits the condition 
to a small extent. 
In Fig. 10 (p. 473) are seen a few curves of the scales of fish from 
various tanks which were in bad condition. The first two curves are from 
two fish from the abundant tank, No. 8 and 9 in the table. In February, 
