134 Professor E. Forbes on Species. 



unlike the individual, it is continued indefinitely so long as 

 conditions favourable to its diffusion and prosperity — that is 

 to say, so long as conditions favourable to the production and 

 sustenance of the individual representatives or elements are 

 continued coincidently with its existence. 



[No amount of favouring conditions can recal a species 

 once destroyed. On this conclusion, founded upon all facts 

 hitherto observed in palaeontology, the value of the application 

 of Natural History to Geological science mainly depends.] 



C. The genus, in whatever degree of extension we use the 

 term, so long as we apply it to an assemblage of species 

 intimately related to each other in common and important 

 features of organisation, appears distinctly to exhibit the 

 phenomenon of centralization in both time and space, though 

 with a difference, since it would seem that each genus has a 

 unique centre or area of development in time, but in geogra- 

 phical space may present more centres than one. 



a. An individual is a positive reality. 



b. A species is a relative reality. 



c. A genus is an abstraction — an idea — but an idea im- 

 pressed on nature and not arbitrarily dependent on man's con- 

 ceptions. 



a. An individual is one, 



/3. A species consists of many resulting from one. 



y. A genus consists of more or fewer of the mantes result- 

 ing from one linked together not by a relationship of descent, 

 but by an affinity dependent on a Divine idea. 



a. An individual cannot manifest itself in two places at 

 once ; it has no extension in space ; its relations are entirely 

 with time, but the possible duration of its existence is regu- 

 lated by the law of its inherent vitality. 



b. A species has correspondent and exactly analogous re- 

 lations with time and space — the duration of its existence as 

 well as its geographical extension is entirely regulated by 

 physical conditions. 



c. A genus has dissimilar or only partially comparable re- 

 lations with time and space, and occupies areas in both, having 

 only partial relations to physical conditions. 



The investigations of these distinctions and relations form 



