ORGANIC EVOLUTION 247 



part having vanished, yet the case is not so hopeless as 

 might at first appear, for the hard parts, although dead 

 parts, are the permanent defences and supports which the 

 living substance has fashioned, in accordance with its needs 

 and hereditary tendencies. The living substance in every 

 group builds its hard parts on architectural lines of its own, 

 and the parts of organisms are so correlated that missing 

 parts may often be inferred from those that are known. 

 The scattered bones of a fossil vertebrate tend to reassemble 

 themselves in the mind of the palaeontologist ; there is but 

 one way in which they will go together consonantly to form 

 a possible organism; finding that, a picture of the living 

 organism arises vividly in his mind; and if he draw it on 

 paper, it is what we call a restoration. 



It would take us too far from the field of our practical 

 studies of living organisms were we to attempt to consider 

 even briefly the vast wealth of knowledge of extinct forms 

 of life that palaeontology has brought to light. For such 

 information recourse must be had to the text books, or to the 

 chapters on palaeontology in general treatises of zoology and 

 botany. We may say of organisms, as, in another sense, 

 the poet Bryant said of men, 



"All that tread 



The globe, are but a handful to the tribes 



That slumber in its bosom". 



Hosts of forms , many of them highly specialized , and 

 some groups once dominant have entirely disappeared from 

 among the living, and the aspect of existing groups has 

 vastly changed during the course of their racial history. 



The imperfection of the palaeontological record pro- 

 ceeds not so much from its being based on hard parts , 

 as from the fact that the more primitive and more 

 significant organisms lack such parts, and are , therefore , 

 dropped from the record, while the more specialized, although 

 having that degree of hardness which renders them best 



