504 HISTORY OF CONCHOLOGY. 



been that the shells were organized parts of the animal, which 

 grew and increased with the latter by receiving nutriment 

 and material from the body ; that there was, in fact, nothing 

 peculiar in the formation of shell, but that its growth de- 

 pended, like the growth of bone, on the circulation of 

 juices within itself, and on the assimilation and addition of 

 new matter. Reaumur was never content with reasoning on 

 a point which experiment alone could solve, and with his 

 usual ability and success he instituted numerous experiments 

 on the subject under review. They were principally made 

 on land snails (Helix), but not restricted to them, for by con- 

 fining fluviatile and marine species, both univalve and bivalve, 

 in baskets framed so as to admit the water, and at the same 

 time prevent the escape of the creatures, he was enabled to 

 show that his theory was applicable to the whole class. He 

 proved in this manner that the shell was enlarged by the de- 

 position of calcareous matter to the edges of the aperture, 

 and that this deposition was made in successive layers ; that 

 there was no increase from the intusception of calcareous 

 matter, no additional increase from any action in the shell 

 itself, but that the whole was a successive transudation from 

 certain parts of the living tenant, to which the shell was an 

 inorganic covering. It was objected to him that snails j ust 

 issued from the egg had as many whorls as the parent, but 

 the falsity of this observation was to Reaumur of easy proof, 

 who found that these young had only one, or not more than 

 a whorl and a-half ; and his theory, divested of the mecha- 

 nical phraseology in which some of its details are explained, 

 remains essentially correct. Besides the establishing of this 

 discovery so important in scientific conchology, Reaumur 

 enriched it with much curious and interesting matter. His 

 inquiry into the mechanism by which the limpets fix them- 

 selves so firmly, and the byssiferous bivalves spin their silken 

 cables ; his accurate description of the structure of the shell 

 of the Pinna ; and his experimental essay on the purple dye 

 of the Buccinum, suggested to him by the excellent paper 

 on the same subject by Mr. Cole, of Bristol, are favourable 

 specimens of his talent for observation, and real additions to 

 the stock of our knowledge, while they captivate us by the 

 elegant and copious style in which they are written, and by 

 the clearness of their details. 



These labours and discoveries, and the high character of 

 their authors, render the conclusion of the 16th, and the 

 beginning of the 17th century, uncpaestionably the most 

 interesting period in the history of conchology. Ray, who 

 discovered the peculiar hermaphroditism of the snail, was 



