14 THE NATURAL HISTORY OF THE COMMON CRAYFISH. 
denote that which the Greeks, ancient and modern, 
signify, by its original, astakos; and does signify 
something quite different. 
Finally, as to why it is needful to have two names 
for the same thing, one vernacular, and one technical. 
Many people imagine that scientific terminology is a 
needless burden imposed upon the novice, and ask us 
why we cannot be content with plain English. In reply, 
I would suggest to such an objector to open a conversation 
about his own business with a carpenter, or an engineer, 
or, still. better, with « sailor, and try how far plain 
English will go. The interview will not have lasted long 
before he will find himself lost in a maze of unintelligible 
technicalities. Every calling has its technical termin- 
ology; and every artisan uses terms of art, which sound 
like gibberish to those who know nothing of the art, but 
are exceedingly convenient to those who practise it. 
In fact, every art is full of conceptions which are 
special to itself; and, as the use of language is to convey 
our conceptions to one another, language must supply 
signs for those conceptions. There are two ways of 
doing this: either existing signs may be combined in 
loose and cumbrous periphrases; or new signs, having 
a well-understood and definite signification, may be in- 
vented. The practice of sensible people shows the 
advantage of the latter course ; and here, as elsewhere, 
science has simply followed and improved upon common 
sense. 
