207 
left side. The pigmentation now gradually disappears 
from the lower side. 
The larve now feed almost entirely on Copepoda, 
with which their stomachs are usually crowded; larval 
Molluses and larval Crustacea are also eaten. After the 
metamorphosis the food is changed, and the small fishes, 
1} to 4 inches, feed largely on various Annelids such as 
Nereis and Pectinaria, on small Crustacea such as M@ ysis, 
and various Amphipods and small Crangons. Later on 
the fish adopts its definitive food, which is mostly Mol- 
lusea, the favourite forms being Cardiwwm, Tellina, Mactra, 
Scrobicularia, Donavx and Mytilus. The character of the 
food changes little during the rest of its life. 
Rate of growth.—A variable time is taken up by the 
changes above described, which were observed in larve 
kept in aquaria. For instance, although the Plaice in 
the Danish seas may spawn as early as November, no 
larve of 12mm. length are taken there till May. They 
therefore require six months to pass through the meta- 
morphosis. Two methods have been adopted for esti- 
mating the rate of growth subsequent to the larval period. 
The most obvious one is to keep a large number of young 
fish in captivity in aquaria, and to observe for as long a 
period as may be possible the changes in body length. 
This method is evidently open to the grave objection that 
the fishes lve under artificial conditions, and these may 
influence their rate of growth. The other method is to 
fish often in waters which contain great numbers of Plaice 
of different sizes, and to deduce the growth rate from the 
grouping of the individuals of different lengths. When 
this is done and the results of measurement of all the 
fishes captured are tabulated, it is seen that those captured 
at any one time may be arranged into several groups in 
each of which the greater number are grouped round cer- 
