INTRODUCTION 3 
classification. It is commonly supposed, at least I have very 
often heard it suggested, that naturalists delight in Latin names, 
and employ them unnecessarily in order to display their own 
erudition. ‘Everybody knows what you mean by a perch,” 
say some: “why in the world do you want to call it Perca 
fluviatilis?”’ The answer comes from afar—from the days 
of Aristotle. The chief obscurity in the luminous discourse 
upon fishes by that penetrating intellect arises from his use 
of temporary and local popular names for the different species. 
It is because such names not only vary from age to age, but 
are applied simultaneously to different creatures in different 
localities, that we have been driven by necessity to the dead 
languages—the languages that have passed beyond all change— 
to secure precise definition. 
Here is an instance of the confusion inevitable in the 
absence of a scientific standard. Most people know a flounder 
well enough—at all events, they think they do. But on the 
south-west coast of Scotland, where flat-fish greatly abound, 
the true flounder is known as the fluke, and the term flounder 
is applied popularly to quite a different fish, the plaice. Hence, 
to avoid confusion, which is the very first step in the advance- 
ment of knowledge, it has been necessary to give each of these 
fish a generic and specific name in an unchangeable language. 
Take an instance from the kindred science of ornithology. 
Among all bird-names there is none, probably, which conveys 
to British people such a clear, familiar image as that of robin. 
Even town-bred children, for whom the greenwood, alas! is 
too often but an unmeaning phrase, have learnt enough from 
picture books to attach the title to a little red-breasted bird 
which spends Christmas with us. But see how different is the 
idea conveyed by the name of robin to that vast branch of 
the English-speaking race beyond the Atlantic. The early 
settler in North America chose to apply this name to a kind 
of thrush (Merula migratoria). And, were there no common 
language wherein ornithologists could confer, science, instead 
