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THE STUDY OF HUMAN IMPLEMENTS AS AN 
AID TO THE APPRECIATION OF PRINCIPLES 
OF EVOLUTION AND CLASSIFICATION 
By E. J. SALISBURY 
E veryone who has attempted to teach the fundamental facts 
with respect to evolution and principles of classification has 
probably found the value of concrete examples in elucidating abstract 
concepts. But whether examples be culled from the animal or vege¬ 
table kingdoms there are always preconceptions in the student’s 
mind with regard to them which tend to obscure the principles to 
be deduced from their study. 
To overcome this difficulty the writer has resorted to the use of 
an analogy which the Editor has asked him to explain in the hope 
that others may find it equally helpful. 
In the choice of such an analogy a wide field is offered us. If 
for example we wished to illustrate convergent evolution, probably 
no better examples could be found than the many isotopes which 
have now been demonstrated by the chemist and physicist possessing 
apparently identical chemical properties but different atomic weights. 
The two types of lead derived from uranium and thorium re¬ 
spectively offer as striking an analogy to the convergent evolution 
of the biologist as could well be found. 
So too the morphologically identical Eucalypts, only separable 
by means of the terpenes which they contain, or the different albino 
Primulas, only distinguishable when analysed by the geneticist, are 
paralleled by the isomeric compounds of the organic chemist. 
The periodic series into which the chemical elements fall and the 
light that has been shed by the study of radio-active substances have 
as profound a significance as the study of the passage from nebula 
to star and each serves to emphasise a particular aspect of the 
evolutionary sequence. Recently the former analogy has been 
developed by Heslop-Harrison in relation to his section-species of 
Rosa (Trans. N.H.S. Northumberland , Durham and Newcastle , vol. V, 
pt. ii, p. 257). 
But though there is scarcely a branch of knowledge that cannot 
contribute something to the comprehension of evolution, especially 
in detail, the progress of development of man’s implements appears 
