THE PERMIAN PERIOD. 641 



sought and less freely received than they merit, because of preva- 

 lent preconceptions as to what must have been the state of the atmos- 

 phere and the type of life, arising from a single unquestioned hy- 

 pothesis of the early state of the earth and its necessary sequences. 

 If alternative views on this fundamental subject are entertained, 

 the psychological conditions will be more felicitous for following to 

 their legitimate conclusions the extraordinary facts of this critical 

 period. 



Because the physical conditions were so pronounced in the salient 

 features of glaciation and aridity, certain questions relative to the 

 life at once arise: (1) Was it possessed of such powers of adaptation 

 that it met its extraordinary environment by accommodating itself 

 to it; or (2) was it destroyed co-extensively with the changes in envi- 

 ronment; or (3) did it elude the adverse conditions by shifting from 

 one area to another as the adverse conditions shifted (hypothetically) ; 

 or (4) did its composite experience embrace all these, and if so, what 

 measure of each? 



The impoverishment of life. — There is no question but that there 

 was a great reduction in the amount of life. In the earlier days of 

 geology, it was commonly held that a complete destruction of all living 

 things on the face of the earth attended this closing period of the Paleo- 

 zoic era, and that a re-creation followed ; for in the state of knowledge 

 of that time, no Paleozoic form was known to occur in the following 

 era. Had it then been known that glaciation pressed upon the bor- 

 ders of the tropics on either side, in the far Orient, and that intense 

 aridity dominated large areas elsewhere, it would have added great 

 strength to the conviction of a universal catastrophe to life. With 

 the progress of investigation, however, no small relief from the adverse 

 data has been found in the discovery that some forms bridged the 

 interval, and in the additional grounds for belief that many others 

 underwent modifications which enabled them to pass it as new types, 

 and in the accumulating evidences that the succession of life was 

 unbroken, though greatly modified. Progressive investigation is still 

 bringing forth more and more evidence of this kind, and reducing 

 the disastrous implications of the record. Not only this ; but wide study 

 brings into view the compensating effects of the strenuous conditions 

 in calling into play the latent powers of adaptation and of resistance 

 of the organisms, and in producing new forms of life. Notwithstand-. 



