114 MARVELS OF FISH LIFE 
illumination, obtained the photographs shown on the 
plates opposite. 
The three illustrations of the plaice hatching were 
obtained between 10 p.m. and 5 a.m. after three days’ 
unsuccessful work ; but I was well rewarded in the end, 
for the movements of the young fish emerging from the 
egg membrane were exceedingly interesting to watch 
as seen on the ground glass of the camera. 
The plaice egg, if rolled between the finger and 
thumb feels quite hard and shot-like, but in due course 
the growth of the delicate larva bursts the egg mem- 
brane, and some part of the little fish protrudes. _ 
In the hatching illustrations, the first photograph 
shows the head and part of the yolk sac protruding. 
In this particular case, the young plaice appeared to 
take a fixed point with its tail, then alternately straigh- 
tening and relaxing its back in quick succession, it 
hammered with its head and shoulders against one side 
of the rent. In this manner, the egg membrane was 
sufficiently torn open to allow of the escape of the 
hatching plaice. 
As opposed to this method of hatching, members of 
the salmon family force themselves out of the egg mem- 
brane with a wriggling movement. 
The second photograph of the plaice hatching 
head first, well illustrates the hammering movement 
described. 
In the illustration of the plaice hatching tail first, 
it will be seen that the median fin which encircles the 
