PRESIDENTIAL ADDRESS. 1 1 9 



genus, :i thin octavo of fifty-nine pages. The fourth edition of 

 this work appeared in 1S70, when it had grown to 214 pages 

 quarto. 



Dr. Lea was a member of most American and many foreign 

 scientific societies. He visited Europe and studied his favorite 

 mollusks at all the museums. There he made the acc|uaintance of 

 Ferussac, Brogniart, Gay, Kiener, and other distinguished men, 

 whose names now sound like echoes from a past epoch. Up to 

 1S74 he continued ever busy on the Unionidte, and the number of 

 new forms, recent and fossil, made known by him amounts to 

 nearlv 2,000. Not content with ficruring: and describing the 

 shells alone, he figured the embryonic forms of thirtv-eight 

 species of Unio, and described the soft parts of more than 300. 

 He also investigated physiological questions, such as the sensi- 

 tiveness of these mollusks to sunlight and the differences due to 

 sex. His observations on the genus Unio form 13 quarto vol- 

 umes, magnificently illustrated. Dr. Lea was president of the 

 American Association for the Advancement of Science in 1S60; 

 he* presided over the Academy of Natural Sciences in Philadel- 

 phia for several terms, and was given the degree of LL. D. by 

 Harvard College in 1853. 



His scientific activity extended over more than sixtv years. 

 He was active in affairs and vigorously participated in those con- 

 troversies in which Say, Conrad, Morton, and others were en- 

 gaged half a century ago. Of these the echoes only have come 

 down to us, but there is plenty of evidence that the battle was 

 often hot and the victory energetically contested. 



Dr. Lea had an intellectual and, in later years, a most vener- 

 able presence. ' He was ever anxious to interest the young in 

 scientific pursuits, and was notably active in charitable and relig- 

 ious enterprises. In his youth he manifested more than ordinary 

 artistic talent, much like his distinguished contemporary, Alvan 

 Clark. 



