The Presidential Address. 
79 
reconstruct genealogies from the surviving remnants of past 
faunas and floras. For the term “affinity” we may now 
substitute the expression, blood-relationship. Thus, taking 
any group of allied forms, such as the species of a genus, we 
say that these have descended from a common ancestral form 
now extinct. The wider the group which we are considering 
the further back in time should we have to go to arrive at 
the point from which the various forms composing the group 
diverged ; in other words, the degree of difference between 
species is a measure of the amount of their divergence from 
a common parent. The science of Palaeontology, which deals 
with the life of the past as preserved to us in fossil remains, 
becomes linked by inseparable bonds to Taxonomy. It is to 
the geological record that we have to appeal to fill up those 
links which are necessary for the completion of our pedigrees. 
How vastly increased in importance becomes the determina¬ 
tion of true morphological affinity—with what surpassing 
interest does Homology become endowed—when we know that 
the structural resemblance of two animals, however externally 
disguised, is due to community of descent from an ancestor 
that lived in the remote ages of geological antiquity. 
Until the publication of the ‘ Origin of Species’ geologists 
had never fully realised the fact that their fossil collections 
represented but an infinitesimal fraction of the whole number 
of animals and plants that had peopled the earth from the 
earliest times. Darwin says on this point:—“ I look at the 
geological record as a history of the world imperfectly kept, 
and written in a changing dialect; of this history we possess 
the last volume alone, relating only to two or three countries. 
Of this volume, only here and there a short chapter has been 
preserved; and of each page, only here and there a few 
lines .” 14 “The crust of the earth, with its imbedded 
remains, must not be looked at as a well-filled museum, but 
as a poor collection made at hazard and at rare intervals .” 15 
When, from the standpoint of modern Geology, we consider 
how small is the chance of the preservation of an animal or 
plant in the state favourable for fossilization, and when we 
14 1 Origin,’ 6th ed., p. 289. 15 Ibid., p. 427. 
