576 HENR V SHA L ER WILLI A MS 



in applying such a statement much confusion and imperfect cor- 

 relation has arisen by failure to recognize wlierein consists the 

 time-value of the fossil. 



Identity of fossils may be wrongly interpreted — a trilobite 

 is a trilobite, it is true, but one trilobite is a Paradoxides and 

 another is PJiacops ; and the one indicates an early period of 

 Paleozoic time, while the latter indicates a much later period. 

 Then, again, PJiacops cristata appeared in the early part of the 

 life history of the genus Pliacops, while PJiacops rana is a later 

 species of the same genus. Thus it is evident that in speaking 

 of identity of fossils one may have in mind the same ciass, the 

 same order, or the same fajnily, genus, or species ; and the time 

 value will differ according to the category of zoological classi- 

 fication to which the identity applies. The time represented by 

 the morphological character of the genus Paradoxides is much 

 shorter in length than that represented by the sub-class Trilobita ; 

 and the period of time represented by the characters of the 

 genus Paradoxides is diverse from that represented by the genus 

 PJiacops. So in regard to all kinds of organisms represented by 

 fossils : the morphological characters expressive of the more 

 comprehensive zoological divisions are of greater antiquity than 

 those of less comprehensive divisions. The time-value of a 

 class character is, in most cases, as long as all the recorded time 

 of stratified rocks ; while the time-value of a species is often 

 not over a tenth of that length. 



In order to discuss these time relations it becomes necessary 

 to make scientific discrimination of the characters of organisms 

 in their time relations. First of all, what is it about the organ- 

 ism which is directly co-ordinate with time ? An answer to this 

 question will be reached by considering the fundamental charac- 

 teristic of organisms — their grozvtJi. The form possessed by 

 any organism living is expressed only as the individual grows 

 or develops from an embryonic or forinless state. The form is 

 acquired by each individual organism ; always by individual 

 development requiring duration of time. This time is the living 

 period of the individual. If every individual developed some 



