Time and the Geological Record 293 



mary. For a reasoned understanding of life and conduct, 

 they must be known in a fullness accessible only by appre- 

 ciative study. The modern sciences treating of biology 

 aflford a volume in which we may learn the general adapt- 

 ability and flexibility of all life forms. We find organized 

 living things continually changing in form by variations 

 which are without end. We find these variations often re- 

 jected after a brief tolerance. Some have served a purpose 

 which has ended. Some have served apparently no purpose 

 or have even been detrimental. Others have been beneficial 

 and we see them recurring, and growing in use ; descending 

 to offspring from parent, to be tried again in a new genera- 

 tion. And then after many generations we see such new 

 features apparently settled and confirmed, in the type which 

 is normal. So long as they are profitable, these new fea- 

 tures may be expected to continue ; yet we see that hundreds 

 of generations can only provisionally fix any form. The 

 length of neck and foreleg of the giraffe is the inheritance 

 of innumerable generations of tree-feeding ancestors; yet 

 it would, we know, slowly disappear if tree feeding ended, 

 and if innumerable generations of progeny found bush feed- 

 ing good, they would develop again the moderate neck from 

 which it was formed. And so it is of the fleet-running ma- 

 chinery and way of living of the deer or horse, which 

 could lapse into the inactive habit of the cow, if many gen- 

 erations of lethargic life made the fleetness useless. So 

 again of the strong winged birds, the carrier pigeon and 

 partridge and wild duck. Their flight is for their way of 

 life; and their wings, which make it possible, would be- 

 come as weak as those of tame fowls, in even a few genera- 



