174 The Science of Life. 



certain fossil sea-urchins permanently retain such features as 

 linear ambulacra and a pentagonal peristome, which characterize 

 the young of their living allies; among Pelecypoda, the stages 

 of early youth in oysters and Pectinidae may be compared 

 with palaeozoic Aviculidae. Among Brachiopods, according to 

 Beecher, the stages which living Terebratulidse pass through 

 in the development of their arm-skeleton correspond with a 

 number of fossil genera. Among completely distinct groups 

 also, ontogenetic characters have been successfully traced. The 

 beautiful researches of Hyatt, Wiirtenberger, and Branco have 

 shown that all ammonites and ceratites pass through a goniatite 

 stage, and that the inner whorls of an ammonite constantly 

 resemble in form, ornament, and suture-line the adult condition 

 of some previously existing genus or other." 



But what the evolutionist would fain have from the 

 palaeontologist, what he wishes for much more than for 

 "evidences of evolution", is some definite information 

 as to the mode and method of organic progress. When 

 we inquire, we find extreme difference of opinion, and 

 no possibility of experiment to change theory into 

 doctrine. To Cope the facts pointed clearly to use- 

 inheritance; to Osborn this is, to say the least, doubt- 

 ful ; to others, there seems no evidence at all suggestive 

 of such a conclusion. To some, the changes of struc- 

 ture observed in the fossil series seem clearly to indicate 

 progressive variation in definite directions, but others 

 point out that any proof of definiteness assumes the 

 series of specimens to be fairly complete, or that we 

 may have lost the initial stages before the indefinite 

 variants were pruned off by natural selection. In short, 

 as usual, we find interpretations where we require cer- 

 tainties. 



As an illustration, however, we shall quote three 

 conclusions from Prof. W. B. Scott's thoughtful and 

 cautious essay on Palaeontology as a Morphological 

 Discipline. 



(a) " Evolution is ordinarily a continuous process of change 

 by means of small gradations" . . . "but this does not imply 

 that a sudden alteration of conditions may not bring about dis- 

 continuity, Q\ per saltum development." 



(b) " Development is, in most instances, direct and unswerv- 

 ing. The rise of new forms, and the decadence and degeneration 



