PALEONTOLOGY 109 



been any upward tendency in their evolution through 

 all the ages, it is hardly possible to measure it. 



And so the living Gasteropods can claim but little 

 superiority in structure over those of the Primordial. 



The same is true of Cephalopods, which are, per- 

 haps, the highest of the invertebrates. The Ortho- 

 cerata existed throughout the Palaeozoic — three- 

 fourths of all geological time — and made no material 

 change in structure. The Pearly Nautilus of to-day 

 is closely like the Nautilus of the Mesozoic, and even 

 the Dibranchs now living are not much higher in 

 structure than the earliest known orthoceras. 



It is indeed most remarkable that if the Primordial 

 animals of these various classes were evolved from 

 lower forms, thus showing great capacity for im- 

 provement in divergent lines, they should uniformly, 

 from their earliest known appearance through all 

 subsequent ages, have made little change in structure, 

 and little or no marked progress in organization. 

 The progress of all these animals prior to the Primor- 

 dial is, I think, inconsistent with the almost total 

 lack of progress since that period, and this lack of 

 progress is inconsistent with the claim that man has 

 been evolved from some Primordial animal. 



I am not here concerned with the origin of species, 

 but with those great changes in structure which the 

 theory of evolution demands in order to derive the 

 highest from the lowest forms. 



Already, in the Primordial, animals had made 

 one-half their total progress in structure, according 

 to Le Conte, but they had widely diverged in struc- 

 ture, so that they represented all the sub-kingdoms 

 except the Vertebrata, and, if the theory of evolution 

 is true, vertebrates must have been there. 



The divergence which has taken place between the 

 sub-kingdoms of invertebrates since the Primordial 



