898 



SCIENCE 



[N. S. Vol. XXVIII. No. 730 



after the earth was once well planted with 

 the rapacious varieties. This adverse con- 

 tingency obtains quite irrespective of the 

 theoretical possibility of such an evolution 

 under favorable conditions, if left undis- 

 turbed. 



A further element should not be over- 

 looked. Before an organic series can be 

 permanently assured, the power of self- 

 propagation must be acquired. What may 

 be the contingencies attending the addition 

 of the self-propagating function to the 

 acquisition of the requisite chemical con- 

 stitution is at present quite beyond de- 

 termination. There may be in this supple- 

 mentary process, if indeed it be a supple- 

 mentary process, as great a liability to 

 predatory arrest, as in the chemical syn- 

 thesis itself. Probably the safest answer 

 which the extreme evolutionist can give to 

 the suggestive question why wholly new 

 orders of living beings have not appeared 

 at frequent intervals in the geologic record, 

 lies in an appeal to the rapaciousness and 

 universality of the attack of organisms 

 already present. 



It is merely as a matter of precaution 

 that these considerations are cited here. 

 It does not seem to us safe to make the 

 unqiialified affirmation that present ter- 

 restrial conditions are wholly incompatible 

 with the natural synthesis of a series of 

 carbon compounds linking the inorganic to 

 the organic if the whole predaceous king- 

 dom were removed so as to leave the or- 

 ganizing agencies unlimited opportunities 

 for interaction for an indefinite period. 

 The purpose of this paper is not to meet 

 a geologic necessity, but merely to con- 

 sider those conditions in the early history 

 of the globe which may be thought to have 

 been specially favorable to organic syn- 

 thesis, irrespective of the question whether 

 the natural evolution of life was wholly 

 dependent upon them or was merely facili- 

 tated by them. The paper is not the result 



of an inquiry into the problem of organic 

 synthesis, as such, but is rather a pre- 

 liminary statement of supposed geologic 

 conditions intended to suggest inquiry in 

 certain lines which do not seem to have 

 been critically pursued. At the same 

 time, the treatment may serve to connect 

 with this chief est of synthetic problems the 

 postulates of the planetesimal hypothesis 

 which have been little discussed in this 

 regard.^ Only a part of the agencies 

 herein suggested as bearing on the syn- 

 thetic process are however peculiar to this 

 hypothesis. In some notable part they are 

 assignable to any mode of origin which the 

 earth may reasonably be supposed to have 

 had. 



The growth of the earth by the plane- 

 tesimal method leaves a rather wide specu- 

 lative range relative to the conditions 

 which prevailed at the stage when life was 

 introduced. At the same time, the hypoth- 

 esis recognizes limitations which shut out 

 certain conditions that have sometimes 

 been thought to be important to the evolu- 

 tion of the higher carbon compounds, 

 notably high atmospheric pressure. Under 

 the older cosmogonies very high atmos- 

 pheric pressures associated with very high 

 temperatures were postulated. Under the 

 planetesimal hypothesis, it is indeed pos- 

 sible and logical to assign to the atmos- 

 phere as great an extent and as high a 

 pressure as the gravity of the earth can 

 control; but the hypothesis, as we hold it, 

 is built on the assumption that molecular 

 activities limit the atmosphere, a principle 

 which, if true, limits it under any hy- 

 pothesis. If the doctrine of Stoney, modi- 

 fied to meet the new advances in physics, 

 is sound, it can not, of course, be violated 

 by any cosmogonic hypothesis without self- 

 destruction. If this doctrine is true, and 

 the earth-mass lacks power to control an 

 ^ Chainberlin and Salisbury's " Geology," Vol. 

 II., 1906, pp. 111-116. 



