PROBLEMS OF DISTRIBUTION AND THEIR SOLUTION. 133 



dental bond, links them together as parts of a whole. To know, for 

 example, that the existing horse walks upon the greatly developed 

 third toe of each foot, to become aware that the horse likewise 

 possesses two rudimentary toes on each foot, are mere facts, 

 valuable enough perhaps in themselves, but useless, so long as they 

 remain isolated, for any higher or philosophical reasoning concerning 

 the horse or any other animal form. Once, however, let these facts 

 be placed in true harmony with other details regarding the equine 

 race, and the science that is, the true knowledge of horses is 

 then constituted. Thus, if we discover that the horses of the present 

 are connected by a complete series of gradations with the horses of 

 the past ; and that we may pass by graduated stages from the one- 

 toed horse of to-day to the five-toed Mesozoic ancestors of the race, 

 we at once rise into the region of a philosophy which, through 

 correlated facts, seeks to teach us the origin of the equine species. 

 If, further, knowing that horses were believed to have first been in- 

 troduced into the New World at the Mexican Conquest, we suppose 

 that in its distribution the horse is a strictly Old World form, that 

 isolated fact tells us but little of the history of the race. Even it 

 we discover that the fossil remains of horses occur in the Tertiary 

 deposits of America as well as in those of Europe, the knowledge ot 

 that fact may certainly enlarge our ideas of the former distribution 

 of horses, but of itself the fact does not place us in possession of any 

 connected details concerning the general history of the form in 

 question. But when, by bringing these varied facts into relation with 

 each other, we seek to construct a pedigree of the equine race, we 

 then illustrate the higher use of our knowledge, in that we cause 

 that knowledge to explain itself. 



Of all the facts of distribution, the same opinion may be expressed. 

 Formerly, to say that a given animal was found in this land or that, 

 was accounted the beginning and end of distributional science. 

 The influence of evolution, and the growth of newer ideas con- 

 cerning the modification of species, have together created for us a 

 literally new science of distribution. The ideas which prevailed a 

 quarter of a century ago regarding the fixity of species, and the 

 consequent fixation within certain limits of their habitats, demanded 

 no further exercise of scientific acumen than that necessary to say 

 from what region any given organism was derived, or from what 

 tracts it was absent. With altered ideas of the constitution of the 

 animal and plant worlds, higher and better because truer concep- 

 tions of the manner and causes of the distribution of life on the 

 globe grew apace. In the days of Edward Forbes, the doctrine of 

 "specific centres" held its own as representing the foremost science 

 of its day and generation. With the dogma of the special and 

 independent creation of each species of living beings left utterly 



