Is 
British Fresh-Water Fishes 
INTRODUCTION 
THERE are few features of human history more startling and 
unaccountable than that intellectual frost which arrested the 
growth of natural science at a point of precocious and pros- 
perous development. In the fourth century before Christ, 
Aristotle laid the foundations of a sound system of zoology, 
based on original research and observation ; a system which 
only required correction and expansion by the co-operative 
labours of succeeding generations of students to embrace all 
living creatures in their right relation to each other. In regard 
to aquatic animals, especially, Aristotle had a very keen discern- 
ment, surprising in a student who, so far as is known to us, 
enjoyed no mechanical aid to vision. He neither confused 
cetacean mammals—whales, dolphins, and the like—with fishes, 
nor eels with serpents, but defined 4ranchie and fins as the 
distinctive organs of true fishes. Aristotle erred in some 
directions, indeed, and came far short of full knowledge in 
others, as every student is liable to err and bound to come 
short ; but we are filled with wonder, not at his limitations, 
but at the scope of his knowledge and the general rectitude of 
his conclusions. 
Yet when Aristotle died, natural science stood still. Men, 
indeed, acknowledged his work as a revelation ; but instead of 
passing the torch from hand to hand, they suffered it to burn 
I 
