184 E. J. Salisbury 
The persistence of primitive types side by side with recent and 
more complex ones is illustrated by the manufacture of flint 
implements by the Tasmanian aboriginals till well on into the nine¬ 
teenth century. Moreover the cause of their survival is the same 
as that which accounts for the persistence of primitive biological 
types in the same area, viz. their isolation. 
Even in the study of geographical distribution the analogy is not 
without value, for the origin and spread of man’s inventions is well 
fitted to illustrate the importance of natural barriers or the relation 
between age and area. 
If we consider the series of species presented by the genus 
Alstroemeria in which some have edge-on leaves occupying a profile 
position whilst others have leaves completely inverted involving a 
still further twist of the leaf base and accompanied by inversion of 
the internal structure, one cannot but ask why the apparently more 
fundamental change has been carried out (viz. complete inversion) 
rather than attainment of the same end by the apparently simpler 
course which an untwisting of the leaf base would have involved. 
For it can scarcely be doubted that Alstroemeria originally had a 
dorsiventral leaf with normal orientation. Allium ursinum illustrates 
the same point, whilst we see it again in the development of cladodes 
as leaves in place of renewed development of the scale leaves 
themselves. 
Such examples, of which other cases might be cited, suggest a 
sort of momentum in evolution, a view which would harmonise with 
orthogenesis as conceived by Eimer. Such a standpoint seems 
more rational than the passive “ law of loss ” postulated by Dollo and 
others but, without arguing the point, it may be mentioned in this 
connection that man’s implements often show a sort of momentum 
in their evolution which is perhaps not without significance for the 
students of phylogenetic sequence. 
In the foregoing the writer has attempted nothing more than a 
mere adumbration of the possibilities of this analogy, but it will be 
evident that it is capable of development according to the needs of 
the teacher and his facilities for illustrating the analogy by means 
of suitable museum types. Its value as a teaching instrument 
largely depends on this latter, but in any circumstances one ventures 
to think that if students of biology occasionally examined anthro¬ 
pological collections from the evolutionary viewpoint they would 
find much to stimulate and more upon which to reflect. 
