THE ORIGIN OF LIFE 87 



of oysters appear, one in Europe and one in America, 

 so far as we know, these molluscs have not ceased to 

 exist, and at least 200 species are reckoned as known 

 in the fossil state. With respect, then, to these oysters, 

 there may be such suppositions as the following, 

 none of which, however, we can prove. 



All these species may have proceeded from one 

 origin, by descent with modification, or the same 

 causes which led to their origination in the Car 

 boniferous may have operated again and again. In 

 like manner the closely allied genera Exogyra and 

 Grypliea, which existed in the Mesozoic age, may 

 have originated from oysters or may have originated 

 independently. The different so-called species of 

 oysters, which are all very variable, and many of 

 which are scarcely distinguishable, may have had, or 

 some of them may have had, independent origins, or 

 they may be all descendants of the same primeval 

 stock, modifying itself from time to time to suit 

 changed conditions. Thus the oyster is equally to 

 us a miracle, whether it has continued to propagate 

 itself without varying beyond the characters of an 

 oyster through all these vast ages, in which case it 

 is a miracle of heredity ; or if from causes to us un 

 known it has been from time to time developed from 

 animals of some other kind or kinds, in which case it 

 is a miracle of transmutation ; or if it has been pro 

 duced repeatedly without any mediate agency, in 

 which case it is a miracle of creation. It is evident 



