Molluscs of the isles Sechelles and Amir antes., 95 



themselves, or to which they serve as nourishment, with 

 those of their own species for reproduction, is of such great 

 importance that, in the common opinion, this single part 

 seems to constitute the science entirely. 



It is to this essential point of the science of molluscous 

 animals, or to their natural history, that the works of M. 

 Dufo will convey a very great number of new facts, which 

 will essentially double their value, when we observe that 

 to acquire these, it was necessary to remain many years in 

 localities suitably chosen, where he might have great abund- 

 ance of molluscous animals ; and, as one of the circumstances 

 most favourable to the reproduction of these creatures in cer- 

 tain localities, is indubitably the distance of human establish- 

 ments, and more especially of civilized man, we see how much 

 enthusiasm it required, and even expence, to maintain one^s 

 self a sufficient length of time in such places. 



To this end M.Dufo, stimulated by his tase for conchology 

 rather than any other motive, without any other mission than 

 the desire of being useful, went and stationed himself in the 

 Archipel des lies Sechelles et Amirantes, which offer a great 

 number of creeks and rocks, of sand beds and shoals, and 

 is seldom visited by navigators ; then having taken with 

 him a few negroes and suitable provision, he was able to 

 devote himself without fear of being interrupted to long 

 and repeated observations on many points of the natural 

 history of conchiferous molluscous creatures, also on the 

 opercules, and the differential shades through which the 

 shells pass during development. 



The first point, so long neglected, and to such a degree 

 that we may intimate its study almost to have commenced 

 in our own day, and by the exertion of one of our friends, 

 has acquired a true value, since it has been demonstrated 

 that we might take advantage of it not only for the dis- 

 tinction of species of which we only possess the shell, but 

 also for the establishment of generic divisions truly natu- 



