INTRODUCTION xill 
light is from in front instead of from above, as in 
the pond. 
Some of the photographs of fish in their natural 
environments—for example, the young thornback ray 
facing page 44—are taken with the camera above the 
water. When taking a photograph of this kind, it is 
necessary to cut off the rays of light from the surface 
of the water, either by means of a shield held at a 
suitable angle, or by means of a tube in which is 
fixed the camera, the end of the tube being under 
the surface of the water. 
The micro-photographs of fish life are taken with a 
special apparatus constructed for the purpose. All the 
illustrations, except those of colour cells, scales and 
teeth, are from living fish, and the photographs showing 
methods of concealment are from straight prints and 
untouched negatives. 
It is possible some may read this book who have 
never previously taken any interest in fish. For their 
information I show a rainbow trout, with the chief 
external features numbered and marked. 
I take this opportunity of thanking Professor Herd- 
man for having enabled me to obtain photographs 
of the developing plaice, and Mr. Richmond, of the 
Surrey Trout Farm, Shottermill, for numerous fish and 
eggs supplied, and for interesting information with 
regard to the salmon family. 
Among others who have assisted me in gathering 
material for this book, I would especially thank Dr. 
