242 EXPERIMENTS ON PERMANENT CHANGE OF FORM IN SPECIES. 



these laws are not limited by the artificial classification of natural- 

 ists. The principle on which Mr. Bakevvell proceeded was this: — 

 He first travelled over England, and part of the continent, to discov- 

 er and select animals of different kinds, possessing certain peculiari- 

 ties of form, and other qualities, which he was desirous to render 

 permanent. By selecting two animals to breed from, which posses- 

 sed the desired qualities in an eminent degree, and afterwards select- 

 ing from their offspring those in which these qualities were most con- 

 spicuous, and breeding again from these, the peculiarities were far- 

 ther increased. By continuing the same selection through four or 

 five generations, he obtained laces that would transmit the same qual- 

 ities permanently to succeeding generations.* 



Some naturalists have maintained, that an additional vertebral bone 

 was amply sufficient to establish a distinct species ; but the number 

 of vertebrae is not invariably the same even in man. In some of 

 the negro tribes, an additional vertebral bone is not uncommon. To 

 apply what has been said to fossil conchology : — The molluscous ani- 

 mals that inhabit and construct their shells, have no internal skeleton, 

 and must, therefore, be susceptible of greater change, and possess 

 greater power of adaptation to circumstances, than vertebrated ani- 

 mals, in which the solid bones present obstacles to any essential de- 

 parture from their original form. 



Let us, however, imagine what is very possible ; that a number of 

 individuals of one species of bivalve or univalve shell, were driven, 

 during a violent storm, into a distant part of the ocean, where the 

 animals could no longer obtain their accustomed food, but were still 

 able to support life by aliment of a somewhat different kind. Let 

 us suppose that the annoyances to which they had before been sub- 

 ject, from natural enemies or other causes, were changed for annoy- 

 ances of another kind. Under these different circumstances, is it 

 not probable that the animals themselves would undergo some change, 

 and modify the construction of their shells in some degree, to render 

 them better suited to ihe new conditions in which they were placed } 

 Thus, in the course of a few generations, we should have a race 

 which conchologists would call a distinct species. 



Where a series of tertiary strata of great depth is exposed to 

 observation, as in the case of the sub-Apennine strata, we have the 



* Mr. Bakewell, of Dishley, was in a considerable degree self-educated, but he 

 possessed a strong original mind, which was enlightened by study and meditation: 

 he was also a man of great moral worth, and was intimately acquainted with Dr. 

 Priestley, Dr. Darwin, and other eminent philosophers who inhabited the central 

 parts of England, towards the close of the last century. The late Countess of 

 Oxford once asked the author of the present work, whether he was related to 

 the Mr. Bakewell who invented sheep. He replied that he was of the same Lei- 

 cestershire or originally Derbyshire family, and that Mr, Bakewell the inventor 

 of sheep said, that " he felt satisfaction, not in having provided for the tables of 

 the rich, but for the families of the labouring classes, to whom a pound of his fat 

 mutton over a dish of potatoes made a cheap and nutritious dinner." 



