METHOD FOR STUDY OF MOLLUSKS. 283 



during these years an incredible energy, of 

 which the history of science offers, perhaps, 

 no other example." 



Among his most important zoological re- 

 searches at this time were those upon mol- 

 lusks. His method of studying this class was 

 too original and too characteristic to be passed 

 by without notice The science of conchology 

 had heretofore been based almost wholly upon 

 the study of the empty shells. T.o Agassiz 

 this seemed superficial. Longing to know 

 more of the relation between the animal and 

 its outer covering, he bethought himself that 

 the inner moulding of the shell would give 

 at least the form of its old inhabitant. For 

 the practical work he engaged an admirable 

 moulder, M. Stahl, who continued to be one 

 of his staff at the lithographic establishment 

 until he became permanently employed at the 

 Jardin des Plantes. With his help and that 

 of M. Henri Ladame, professor of physics and 

 chemistry at Neuchatel, who prepared the del- 

 icate metal alloys in which the first mould was 

 taken, Agassiz obtained casts in which the 

 form of the animals belonging to the shells 

 was perfectly reproduced. This method has 

 since passed into universal use. By its aid he 

 obtained a new means of ascertaining the re- 



