“ORIGINATION OF SELF-GENERATING MATTER AND 
PEEING OENCE, OF ARIDITY WPRON TEs 
EVOLUTIONARY DEVELOPMENT 
DRe DD. MACDOUGAL 
XV 
Any attempt at an interpretation of a desert landscape, with its 
diversity of forms, isolation of individuals, and scarcity of organic 
matter in the soil, leads inevitably to a consideration of the theoret- 
ical conditions which would be necessary in the origination of the 
physical basis of life, its development into organisms known to us 
in the living and fossil state, and also of the possibilities of the oc- 
currence of a re-generation at the present time. 
From almost every excursion which the biologist has made into this 
inviting field of speculation on which he has called to his aid various 
extreme or unusual intensities of the factors to be taken into account, 
he has been ruthlessly recalled by the geological historian with the 
reminder that the general composition of the atmosphere, its pres- 
sure, the temperatures, and other conditions prevalent on the earth’s 
surface were uniform and continuous with those now encountered 
and not widely different, in their total departure, in any stage of 
terrestrial development in which life might have originated. 
Now we are not able to discover that living or self-generating 
matter is actually being formed anew on the earth’s surface at the 
present time, and in the absence of positive evidence we are com- 
pelled to say that all life now in existence must have descended from 
forms which had their ultimate origin in other times and under 
other conditions than those now prevalent. 
A consideration of the phyletic aspects of fossil and living forms 
of plants yields but little, which might serve as an indication of the 
conditions under which the earlier forms developed. Even the earliest 
remains include such advanced types as the ferns and cycads. The 
amount of progress represented by the derivation of the gameto- 
petalous seed-plants from these, in comparison with the preceding 
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