338 THE HISTORY OF BIOLOGY 



world of the past and that of the present? He has tried to give the answer 

 in a survey of the process of the earth's development through the ages, which 

 forms the introduction to his Kecherches and which became his best-known 

 and his most discussed work. Herein, basing his argument on material de- 

 rived from the finest observations of earlier times, supplemented by his own, 

 he seeks to prove that the changes in the character of the animal world have 

 been caused by great catastrophes undergone by the earth's surface in pre- 

 historic times. He at once takes it for granted that these changes had the 

 character of violent catastrophes; that they were violent he considers to be 

 established by the fact that stratifications which, judging from the nature 

 of the fossils, have demonstrably taken place in the sea, are now found on 

 the one hand elevated to enormous heights and on the other hand over- 

 thrown and inverted. That all this took place with great rapidity is obvious 

 to his mind, not only from the sharp lines of demarcation shown by the 

 various strata, but also from the fact that many of them contain such extraor- 

 dinarily numerous animal remains that it can only be assumed that they 

 died a sudden death as the result of upheavals which obliterated all life for 

 the time being. The assumption of such catastrophic changes on the earth's 

 surface also affords, in Cuvier's opinion, the best explanation as to why the 

 animal species of ancient times have disappeared and been succeeded by new 

 and entirely different forms. And as a further confirmation of this assump- 

 tion he adduces the fact that most nations possess legends which tell of a 

 mighty catastrophe, a flood that drowned all living creatures, and in which 

 undoubtedly the mammoth and the other great land-animals living in 

 Europe in earlier times perished. 



His catastrophe theory 

 It is this universally known "catastrophe theory" that without doubt 

 brings out both Cuvier's strength and his weakness as a natural-scientific 

 thinker. He does not, however, deserve any very severe censure for the ac- 

 tual theory of these vast volcanic upheavals, with their resultant inunda- 

 tions; the geological material available for observation was still somewhat 

 scanty and was, moreover, as far as French research was concerned, largely 

 gathered from the Alps, with their greatly subverted formations, which 

 even to this day are difficult to interpret, and which are peculiarly likely 

 to induce a belief in violent upheavals. But there undoubtedly existed in 

 Cuvier a very pronounced tendency to pursue the theories he had once set 

 up to their uttermost conclusions — a tendency which may well be at- 

 tributed to his marked aptitude for the formal side of science. Thus, he ex- 

 pressly declares that each stratum has its definite fossil species, which are 

 characteristic of it and do not exist elsewhere; the catastrophes that took 

 place entirely eradicated all then existent species; never has a species sur- 

 vived from one period to the next, so that species found in the form of 



