VOL. II.] Studies Among MoUusks. ^ S^? 



1. • The mechanical impulse to construct a shell as an outer cov- 

 ering for the protection of the animal's body. 



2. The artistic impulse to decorate the external surface of the 



hell. 

 This second or artistic impulse I divide as follows: 



a. The impulse to ornament the external surface of the shell by- 

 varied designs of sculpturing. 



b. The impulse to ornament the external surface of the shell by 



regular artistic colored designs. 



On account of their brilliant colors and the dazzling external 

 polish of many shells they have been truly called the ' ' Butterflies 

 of the Sea,' ' and have always occupied a conspicuous place in the 

 homes of the rich and poor alike, in the cabinets of the mere 

 curio collector, and in the great collections of natural history in all 



the civilized countries. 



The animals of the oyster, mussel, and many kinds of clams, as 

 well as the animals of many univalves, have supplied both civilized 

 and savage people with an abundance of wholesome and nutritious 

 food for ages, while their shells have been utilized in various ways 

 for ornamental and useful purposes. From a geological point of view 

 the work of mollusks in past ages is recognized as having effected 

 great changes in the earth's strata, and they might be called the 

 great lime gatherers of the world, for their shells form the basis of 

 the vast limestone, marble and chalk formations that constitute so 

 large a proportion of many mountain ranges that "rib" the sur- 

 face of the globe. 



Notwithstanding these facts and the conspicuous manner in which 



mollusks have displayed their instincts, no collection, nor a part of 

 any collection, so far as I know, except my own, has been especially 

 arranged to display the mechanical instincts of the moUusk,^ or the 

 progressive development of the shell, from the rude beginning, an 

 aggregation of the few particles of hmy matter such as we find un- 

 der th'e mantle of some of the slugs and ending with the most com- 

 plicated and perfect shells. Neither have especial efforts been made 

 to exhibit the progressive development of what I have called the 

 artistic impulse by arranging a series, first, to represent the de- 

 velopment of the sculpturing by commencing with the plain smooth 

 forms and ending with those ornamented externally with elaborate 

 spines and fringes; and second, by arranging a series to represent 



