CLARKE— THE AGE OF THE EARTH. 273 



could justify the great labor they have exacted, were it not for the 

 important accessory facts they have eHcited. 



There seems to be no effective reason or very good philosophy in 

 declaring, as some of our writers have been wont to do, that all life 

 is one life. We seem to have really established the polyphylogeny of 

 several races not only in the lower phyla of animals and plants, but 

 among the vertebrates, and in the thought of competent authority, 

 even to the inclusion of man, and we assign these like products to a 

 differently governed and directed inheritance emanating from fixed 

 points in evolutionary history. This is an enlarging point of view in 

 the interpretation of past life, and admitting its general effectiveness 

 we can conceive and can justify a concurrence of physical energies 

 which need not, and indeed should not logically, be restricted to some 

 single outburst and some single definite moment in earth history. 

 This intimation is that life itself may be polygenetic, though we would 

 not have it interpreted as applying to the reiterative appearance of 

 inceptive life through the ages, which is an old conception that still 

 awaits its justification ; it is rather only the precise implication of a 

 terrestrial condition so controlled that by the intersection of the 

 requisite forces life came into being at the points rather than at the 

 point of such intersection — a crude way of stating it, perhaps, but it 

 is an intimation of my meaning. 



When we gaze upon some of Walcott's Burgess Pass fossils, see 

 the extraordinary intricacy of their anatomy, as, for example, the 

 crustacean Burgessia, with not merely the delicately toughened parts 

 of its exterior, but the evidence of internal organs of great refinement, 

 the lobulation and venation of renal organs; and, in the trilobite 

 Neolenus, the multiplex delicacy of gills and swimming or walking 

 organs, the effective impression is that, as between such creatures and 

 their nearest allies and perhaps their offshoots of to-day, there is no 

 difference in degree of specialization of structure, no progress in 

 perfection of organic function. Indeed, we may even go further; 

 modern allies of these creatures are in close straits of adjustment to 

 their own physical surroundings, which are too often indicative of 

 the surrender of progress, and to this I shall again make reference. 

 But the Walcott fossils are from the Middle Cambrian, almost the 



