THE BEGINNINGS OF LIFE. 627 



pools y as much power has been needed to raise the one 

 as the other, and there is no a priori reason why the 

 forces which have grafted on the insect type the 

 features and powers of an intelligent bee should not 

 go on to work the same type into something possessing 

 powers and qualities as full, as great, and as varied as 

 those which we ourselves possess/ 



The vertebrate type itself is, moreover, subdivided 

 into many subordinate types, each of which goes along 

 its own lines of development and differentiation, so 

 that there is no trace of any single and general pro- 

 gression towards the perfection of that mammalian 

 branch, of which Man forms the head and crown. As 

 we have already stated. Fishes, Amphibia, and Reptiles 

 of the most divergent forms have been abundantly pro- 

 duced, departing in the most striking manner from 

 one another and from the general vertebrate plan. Whilst 

 amongst Birds also, such specializations of the respi- 

 ratory system, of the organs of locomotion, and of the 

 integumentary system have taken place, that the type 

 on which Man's body has been evolved has, in these 

 respects, been left far behind. Doubtless, therefore, if 

 the conditions had been suitable, the progenitors of the 

 quadrumanous race might have given rise to all that has 

 appeared along this line of development far back in the 

 depths of geologic time and wholly irrespective of the 

 multitudes of aberrant forms of vertebrate life which 

 have flourished since the Silurian epoch. 



There is, indeed, no small amount of evidence de- 



S S 2 



