FOSSIL PEDIGREES 123 



age and metamorphosis, the number of distinct fossil species 

 will undergo considerable shrinkage. Nor must we overlook 

 the possibility of environmentally-induced modifications. 

 Many organisms, such as mollusks, undergo profound altera- 

 tion as a result of some important, and, perhaps, relatively 

 permanent, change in their environmental conditions, though 

 such alterations affect only the phenotype, and do not involve 

 a corresponding change in the specific genotype, i.e, the 

 germinal constitution of the race. 



In the degree that these considerations are taken into ac- 

 count the number of "extinct" fossil species will diminish and 

 the number of "persistent" species will increase. This is a con- 

 summation devoutly to be wished for, but it means that 

 hundreds of thousands of described species must needs 

 be reviewed for the purpose of weeding out the dupli- 

 cates, and who will have the knowledge, the courage, or even 

 the span of life, necessary to accomplish so gigantic a task? 



But so far as the practical purposes of our argument are con- 

 cerned, the accepted list of persistent types needs no ampli- 

 fication. It suffices, as it stands, to establish the central fact 

 (which, for the rest, is admitted by everyone) that some gen- 

 eric and even specific types have remained unchanged through- 

 out the enormous lapse of time which has intervened between 

 the deposition of the oldest strata and the advent of the present 

 age. Our current theories, far from diminishing the significance 

 of this fact, tend to intensify it by computing the duration of 

 such persistence in millions, rather than in thousands, of 

 years. Now, whatever one's views may be on the subject of 

 transformism, this prolonged permanence of certain genera and 

 species is an indubitable fact, which is utterly irreconcilable 

 with a universal law of organic evolution. The theory of 

 transformism is impotent to explain an exception so palpable 

 as this ; for persistence and transmutation cannot be subsumed 

 under one and the same principle. That which accounts for 

 change cannot account for unchange. Yet unchange is an 

 observed fact, while the change, in this case, is an inferred 



