IV.] INTRODUCTION. Ixiii 



inorganic substances are called into requisition, and 

 these again are supplied and renewed from decayed par- 

 ticles of once living matter. Thus a never-ending cycle 

 of waste and renewal takes place^ in accordance with the 

 beneficent design of the Author of all things ! 



The principal use which the MoUusca subserve^ so 

 far as man is concerned, is to supply him, directly and 

 indirectly, with an abundance of food. It is true that this 

 kind of food is not so grateful to us in a civilized as in 

 an uncivilized state ; but one of our most favourite lux- 

 uries is derived from this source, and the oyster, fortu- 

 nately, inhabits those regions where civilization has 

 attained its present height of perfection. Many other 

 kinds of shell-fish, such as scallops and cockles, are not 

 less wholesome than the king of the Mollusks, and are 

 by no means to be despised ; and the ormer (Haliotis 

 tuberculata) is reckoned a delicacy in the Channel Isles, 

 when properly cooked. The salt flavour which is so 

 much relished by a maritime population is imparted by 

 all the marine MoUusca. The quantity (amounting to 

 many hundreds of tons) of whelks, mussels, and peri- 

 winkles which is every year disposed of in Billingsgate 

 market alone is almost incredible ; and there is no 

 seaport or adjoining tract of country, especially in the 

 manufacturing and mining districts, but has a consider- 

 able traffic carried on within it by a numerous and in- 

 dustrious class of itinerant dealers in such wares. On 

 many parts of the Scotch and Irish coasts shell-fish form 

 a considerable portion of the food of the poorer inha- 

 bitants; and in a few of our more remote and almost 

 inaccessible islets (such as Fair Isle and some of the 

 Western Hebrides) positive starvation would ensue in 

 winter, if it were not for these unfailing and easy sup- 

 plies. In an indirect way, the MoUusca contribute still 



