152 GEOGRAPHICAL DISTRIBUTION OF THE MOLLUSCA. 



description and figuring of shells lately made known chiefly 

 falling into the hands of dealers, * * * or of persons employed 

 by dealers, who select for their purpose those who are ready to 

 fall into their views and make as many new species as possible. 

 * * * A shell with a new name is much more valuable in a 

 pecuniary point of view than one with an old and well-known 

 name. The value dealers attach to new names is proved by an 

 incident that occurred to myself a few days ago, when a dealer 

 offered me a new Volute for ten guineas. I said it was not new, 

 onl}'^ a slight variety of a well-known species. At length he 

 admitted that he had nine specimens of the "Volute, and ended 

 by offering to present me with the best of the series if I would 

 describe it as a new species. I am told that at length he found 

 a person to fall into his views, and sold all his specimens at or 

 above the price first mentioned." 



GEOGRAPHICAL DISTRIBUTION OF THE 

 MOLLUSCA. 



Living beings are not distributed at hazard through the 

 depths of the waters and over the surfaoe of the earth, but each 

 species occupies a determined area and has a distinct geograph- 

 ical distribution. In searching for the causes of this law, physical 

 conditions have been first thought of; time, also, is one of the 

 greatest factors, evidently ; and the laws of variation or adap- 

 tability, as yet so little understood, will serve to cast much light 

 on the problem : but after all these factors and all the deducible 

 consequences are fully before us there is still the great question 

 of origin to be considered ; and for this we are forced to accept 

 one of two pure hypotheses : either that centres of creation exist 

 by God's will and independent of physical conditions, or that 

 diverse beings, however isolated in distribution, are all the 

 descendants of a common ancestral type, and have therefore 

 probably been derived from a unique creation. The latter 

 hypothesis is the most fashionable at present, because in this > 

 age man observes rather than marvels, and it is more satisfactory 

 to the human mind to be able to account for things being as we. 

 find them than to refer their existence to the more or less imme- 

 diate intervention of an unknown and unknowable power. 

 Perhaps the development theory has done more to give us a 

 truly philosophical view of nature than any other hypothesis 

 has ever done, but there can be no doubt that many of its prin- 

 cipal advocates have allowed their judgment to become dazzled 

 by its very brilliancy, and in accepting as facts merely speculative 

 propositions, have discovered an amount of credulity quite equal 



