36 EVOLUTION 



And again, since the whole history has been 

 unearthed, we see evolution before our eyes. 

 The particularly interesting feature is that 

 there are four or so primitive forms which 

 are very like one another, and that each of 

 these is the starting-point of a series the 

 termini of which are very different. The 

 contrast between the beginning and the end 

 of a series, e.g. between a high spiral and a 

 flat spiral, is often so striking that no one 

 would hesitate in calling them distinct species. 

 Yet they are connected by a long series of 

 fine gradations. 



Some are surprised that such series are not 

 commoner if Evolution has been the mode of 

 the becoming of things; but they have not 

 adequately understood how great are the odds 

 against the preservation of such records. 

 Only hard parts make good fossils; only cer- 

 tain kinds of deposits make suitable tombs; 

 many rocks have been unmade and re-made 

 several times; these and many other facts 

 enable us to understand " the imperfection 

 of the geological record." As Darwin said, 

 we must 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 



