THE RISE AND PROGRESS OF PALEONTOLOGY. 167 



them to assume without hesitation, the remains of animals and plants ? 

 Or are they, as was so generally maintained in the fifteenth, sixteenth, 

 and seventeenth centuries, mere figured stones, portions of mineral 

 matter which have assumed the forms of leaves and shells and bones, 

 just as those portions of mineral matter which we call crystals take on 

 the form of regular geometrical solids ? Or, again, are they, as others 

 thought, the products of the germs of animals and of the seeds of 

 plants which have lost their way, as it were, in the bowels of the 

 earth, and have achieved only an imperfect and abortive develop- 

 ment ? It is easy to sneer at our ancestors for being disposed to reject 

 the first in favor of one or other of the last two hypotheses ; but it is 

 much more profitable to try to discover why they, who were really not 

 one whit less sensible persons than our excellent selves, should have 

 been led to entertain views which strike us as absurd. The belief in 

 what is erroneously called spontaneous generation that is to say, in 

 the development of living matter out of mineral matter, apart from 

 the agency of pre-existing living matter, as an ordinary occurrence at 

 the present day which is still held by some of us, was universally 

 accepted as an obvious truth by them. They could point to the arbo- 

 rescent forms assumed by hoar-frost and by sundry metallic minerals 

 as evidence of the existence in nature of a " plastic force " competent 

 to enable inorganic matter to assume the form of organized bodies. 

 Then, as every one who is familiar with fossils knows, they present 

 innumerable gradations, from shells and bones which exactly resemble 

 the recent objects, to masses of mere stone which, however accurately 

 they repeat the outward form of the organic body, have nothing else 

 in common with it ; and, thence, to mere traces and faint impressions 

 in the continuous substance of the rock. What we now know to be 

 the results of the chemical changes which take place in the course of 

 fossilization, by which mineral is substituted for organic substance, 

 might, in the absence of such knowledge, be fairly interpreted as the 

 expression of a process of development in the opposite direction from 

 the mineral to the organic. Moreover, in an age when it would have 

 seemed the most absurd of paradoxes to suggest that the general level 

 of the sea is constant, while that of the solid land fluctuates up and 

 down through thousands of feet in a secular ground-swell, it may well 

 have appeared far less hazardous to conceive that fossils are sports of 

 Nature than to accept the necessary alternative, that all the inland re- 

 gions and highlands, in the rocks of which marine shells had been 

 found, had once been covered by the ocean. It is not so surprising, 

 therefore, as it may at first seem, that, although such men as Leonardo 

 da Vinci and Bernard Palissy took just views of the nature of fossils, 

 the opinion of the majority of their contemporaries set strongly the 

 other way ; nor even that error maintained itself long after the sci- 

 entific grounds of the true interpretation of fossils had been stated, in 

 a manner that left nothing to be desired, in the latter half of the sev- 



