298 NATURAL HISTORY. 



guished from one another and from the types which they 

 connect. Mr Darwin has met this difficulty by pointing 

 to the great * imperfection of the palaeontological record/ 

 the fossil forms known to us doubtless forming only an 

 insignificant fraction of those which once existed. This 

 argument is entitled to receive great weight ; but it does 

 not sufficiently account for the general absence of gradu- 

 ated intermediate forms. This, however, is a point which 

 cannot be further discussed here, and upon which each 

 investigator will decide, in one sense or the other, accord- 

 ing to the particular direction in which he may be led 

 by his studies. 



(4) It is, again, assumed upon the theory of natural 

 selection, that 'variation' among the individuals of a 

 species is indefinite, both in amount and direction. It 

 would appear that the theory of the origin of species 

 by means of natural selection requires a belief in the 

 ' omnifarious ' nature of individual variation. The action 

 of 'Natural Selection' would, of course, still go on, even 

 supposing variation to be strictly limited in amount; 

 but in this case it is hardly conceivable that our existing 

 species should owe their origin to natural selection, as 

 the principal or sole factor in their production. On 

 the contrary, it seems necessary to suppose that variation 

 affects, or may affect, all parts of the organism, and 

 that there are no limits to the extent of its operation, 

 though the single steps of the process are small in amount. 

 We have, however, no positive evidence which would 

 enable us to assert, as a scientific fact, that variation 

 is thus omnifarious and indefinite. The evidence actually 

 in our possession is admittedly small, because it only 



