XX INTRODUCTION. 



With such evidence, there is no room to doubt the 

 real existence of the pores mentioned by Reaumur ; 

 but, lest it should be supposed that these pores do 

 not perform the functions ascribed to them, let us 

 see whether an experiment will not confirm the 

 reasoning. If a portion of the shell be removed 

 opposite the black rays, and the new piece become 

 black ; if another portion be removed between the 

 rays, and this be renewed of a colour different from 

 the bands, it must be allowed that these parts 

 perform the office ascribed to them by Reaumur. 

 Now this is exactly the fact : the new shell which is 

 formed on the collar, opposite the brown, or black 

 rays, is itself brown or black ; that which is formed 

 between the rays, is white, or citron ; and that 

 which is renewed on other parts of the body will be 

 white. The same thing happens in all other shells, 

 marine, freshwater, or terrestrial, that are remarkable 

 for their colours. We have not indeed experiments 

 to illustrate every case ; but what has been done is 

 fully sufficient to warrant the conjecture, that the 

 same phaenomenon will be extended to all species of 

 shells. 



We are not, however to conclude, from what has 

 been said of the formation of the rays, which orna- 

 ment certain species, that it is a necessary conse- 

 quence that all shells should be streaked ! On the 

 contrary, we find the surface of some of an uniform 



