248 SPECULATIVE SCIENCE 



as it now does, and that the planetary system contains an inex- 

 haustible motive power, by which the vast labour of the system 

 has been and can be maintained for ever. We have endeavoured 

 to meet the main objections to these views, and conclude that 

 countless ages cannot be granted to the expounder of any theory 

 of living beings, but that the age of the inhabited world is proved 

 to have been limited to a period wholly inconsistent with Darwin's 

 views. 



Difficulty of Classification. It appears that it is difficult to 

 classify animals or plants, arranging them in groups as genera, 

 species, and varieties ; that the line of demarcation is by no 

 means clear between species and sub-species, between sub- 

 species and well-marked varieties, or between lesser varieties 

 and individual differences ; that these lines of demarcation, as 

 drawn by different naturalists, vary much, being sometimes 

 made to depend on this, sometimes on that organ, rather arbi- 

 trarily. This difficulty chiefly seems to have led men to devise 

 theories of transmutation of species, and is the very starting- 

 point of Darwin's theory, which depicts the differences between 

 various individuals of any one species as identical in nature 

 with the differences between individuals of various species, and 

 supposes all these differences, varying in degree only, to have 

 been produced by the same causes ; so that the subdivision 

 into groups is, in this view, to a great extent arbitrary, but may 

 be considered rational if the words variations, varieties, sub- 

 species, species, and genera, be used to signify or be considered 

 to express that the individuals included in these smaller or 

 greater groups have had a common ancestor very lately, some 

 time since, within the later geological ages, or before the primary 

 rocks. The common terms, explained by Darwin's principles, 

 signify, in fact, the more or less close blood-relationship of the 

 individuals. This, if it could be established, would undoubtedly 

 afford a less arbitrary principle of classification than pitching on 

 some one organ and dragging into a given class all creatures 

 that had this organ in any degree similar. The application of 

 the new doctrine might offer some difficulty, as it does not 

 clearly appear what would be regarded as the sign of more or 

 less immediate descent from a common ancestor, and perhaps 



