183 
varieties of the same losen and —— more so between dif- 
ferent — If it not so, varieties and species would 
after a time become indistingvishably blended so as to lose 
their ey characters. is infertility in crossing varies 
i i less 
the MN and also with certain aboriginal inhabitants of 
Amer: It cannot be said that there is any appreciable 
littoral portions se Australia that, er to Prof. 
ate in his above quoted adio since the Pluvial Epoch, 
has gained accessions to its flora from the Indo-Malay pro- 
vince. 
above observations respecting a few of the conditions 
of life and customs of the Australian aborigine 
sh 
tionary progress, it does not at all follow “that it was because 
it had no evolutiona power. Such a condition may ee con- 
sidered as non-existent in Bor Where no progress 
it is because the forces are en e antagonistic, 
ibri It is 
to variability. The familiar Ventes of t he parr 
of forces will make clear what is meant. Let A e a 
of intergenerants set in motion by a force BA (variability) 
in the dırection of X (evolution). If two other forces Ki 
e 
Ns. may have an hs ting or a retarding effect on motion 
according as to whether their line of action is the same as, or 
