theory ; and adds : “ Here he is speaking of arbitrary conditions, and the 
result depends on those conditions being maintained. Mr. Darwin will tell 
you the same law holds good in nature ; if the conditions be maintained, 
then the variation will remain. It is the same with arbitrary alterations as 
with natural alterations.” No doubt. Yet how does this militate against 
my argument, that varieties cannot be converted into species ? It appears to 
me that no circumstances whatever can do this. Remit the conditions, 
whether natural or artificial, and the variety at once fails. But will the 
species ? I conceive not. Alter the conditions of existence which surround 
the Negro, and the Negro will die out — not the man. The perpetuation of 
the various races of man is no proof as to whether they are either varieties or 
species. An aggregation of varieties will form a species. Could every 
variety be extinguished, the species would be at an end. But the subject is 
too extensive for further discussion here. 
I have to thank the Chairman for correcting an assertion I made on crys- 
tallography. I said all crystals had plane surfaces. Mr. Mitchell refutes it, 
and says, “ There are a few crystals with curved surfaces : the diamond has 
curvilinear surfaces. Why the diamond and one or two others should present 
that variation is not quite clear ; but that is a fact.” My knowledge of 
crystallography is extremely limited ; though directly after having said that 
all crystals had plane surfaces, I added, “ pseudomorphous forms arise ; but 
the laws of crystallography are, for all practical purposes, irrefragable ” ; 
showing that I was not altogether unaware of occasional deviations, though 
certainly unaware that the diamond was — more than this — a constant 
exception. 
