THE OYSTER, 6/ 



plan, we infer, just as the philologist does, that they 

 are the divergent descendants of a common ancestor, 

 from whom they have inherited the features which 

 they have in common. 



The philologist is sometimes able to verify his con- 

 clusion by the proofs which have been preserved in 

 books and inscriptions, and he regards this as evidence 

 that, in other cases where no such record is preserved, 

 his results are equally trustworthy. 



Occasionally the student of comparative anatomy, 

 lik-e the student of comparative grammar, finds a fossil 

 form which unites in itself the characteristics of several 

 widely separated descendants, and is thus enabled to 

 test and to verify the conclusions which he has reached 

 by comparative study. 



In this way, through the study of details too numer- 

 ous and minute to be described here, it can be shown 

 that the oyster is descended from a mollusc which 

 was furnished with locomotor organs and sense organs, 

 and which wandered about in search of food, and had 

 altogether a much wider and more varied life than that 

 of the oyster. Its gills were very simple and were 

 nothing but breathing organs, and the many uses 

 which they serve were provided for by distinct organs. 



Very long ago, as we measure time, but quite late 

 in the history of the mollusca, as the continental areas 

 were elevated and became covered with terrestrial 

 vegetation, and fringed by bays and sounds of brackish 

 water, it gradually became modified in such a way as 

 to fit it for life in these estuaries. Its locomotor organs 

 and its organs for discovering and capturing food 

 were gradually lost, as it learned to feed upon the 



