A REMARKABLE ANTICIPATION, ETC. 293 



tained to be characteristic of the vegetable kingdom as well 

 as the animal. Thus the species of a family or genus are 

 often distributed round a centre " which seems to be the 

 principal focus or favourite seat of the tribe," from which 

 the branches diverge in various directions. The particular 

 species, when compared, can be referred to "one type of 

 organization ". The slighter differences between them 

 "seem to lose themselves in the sameness of form be- 

 longing to the genus, and even suggest a suspicion that 

 they all proceeded from one original. The phaenomena 

 of resemblance must have had their sufficient reason as 

 well as those of diversity." He then inquires whether the 

 explanation is to be found in the action of "some slight 

 modification in the productive causes " which stamped the 

 genus at its first appearance " with all these specific diversi- 

 ties " ; or whether on the other hand a uniform genus was 

 first created which " afterwards became diversified by the 

 influence of external agents". He concludes that the 

 former of these alternatives is more strongly indicated by 

 the knowledge of his time. 



" Whichever of these suppositions may be true in point 

 of fact, the separation of families and genera into particular 

 species, and the distribution of these species to particular 

 habitations, according to their physical properties, is evi- 

 dently a part of the provision of nature for replenishing 

 the earth with organized inhabitants, placed everywhere 

 according to the congruity of soils and temperatures, 

 with their structure and habitudes. 



" But why is it to be supposed that the influence of this 

 law of adaptation has stopped here? Is it not probable 

 that the varieties which spring up within the limits of 

 particular species, are further adaptations of structure to 

 the circumstances under which the tribe is destined to exist.-* 

 Varieties branch out from the common form of a species, 

 just as the forms of species deviate from the common type 

 of a genus. Why should the one class of phenomena be 

 without end or utility, a mere effect of contingency or 

 chance, more than the other ? 



" There are indeed many instances in which we can 



