CiiAP. X. PRECEDING AND PRESENT CHAPTER. 321 



ancient and recent, make tog-ctlier a (c\v f^rand classes ; for all 

 arc at least thus far connected by generation. We can undci'- 

 stand, from the continued tendency to divergence of character, 

 why the more ancient a form is, the more it gcnc^rally differs 

 from those now living; why ancient and extinct forms often 

 tend to fill up gaps between existing forms, sometimes blend- 

 ing two groups, previously classed as • distinct, into one ; but 

 more connnonly bringing them only a little closer together. 

 The more ancient a form is, the more often it stands in some 

 degree intermediate between groups now distinct; for the 

 more ancient a form is, the more nearly it will be related to, 

 and consequently resemble, the common progenitor of groups, 

 since become widely divergent. Extinct forms are seldom direct- 

 ly intermediate between existing forms ; but are intermcfhate 

 onl}' by a long and circuitous course through other extinct and 

 difl'erent forms. We can clearly sec why the organic remains of 

 closely-consecutive formations are closely allied ; for they are 

 closely linked togetlier by generation. ^Ve can clearly see why 

 the remains of an intermediate formation are intermediate in 

 cliaracter. 



The inhabitants of each successive period in the world's 

 history must have beaten their predecessors in the race for life, 

 and are, in so far, higher in the scale of Nature, and tlieir 

 structure has generally become more specialized ; and this may 

 account for the common belief held by so many paleontolo- 

 gists, that organization on the whole has progressed. Extinct 

 and ancient animals resemble to a certain extent the embryos 

 of the more recent animals belonging to the' same classes, and 

 this wonderful fact receives a simple explanation according to 

 our views. The succession of the same types of structure with- 

 in the same areas during the later geological periods ceases to 

 be mysterious, and is intelligible on the principle of inlierit- 

 ancc. 



If, then, the geological record be as imperfect as many be- 

 lieve, and it may at least be asserted that the record cannot be 

 jiroved to be much more perfect, the main ol)jections to the 

 theory of natural selection are greatly diminished or disappear. 

 On the other hand, all the chief laws of paleontology plainly 

 jiroflaim, as it seems to me, that species have been produced 

 by ordinary generation: old forms having been supjilanted by 

 new and imjjroved forms of life, the products of Variation and 

 the Survival of the Fittest. 



