EVIDENCE FROM PALAEONTOLOGY 83 



unfortunate that many of these almost or entirely 

 missing types are precisely those which would be 

 most useful in the investigation. For any organism 

 to be preserved and discovered, it is almost essential 

 that it should have been fairly common and abund- 

 ant when living and that is the probable reason why 

 the beginning of so many genealogical lines should be 

 lost in obscurity. 



() Of the innumerable fossil forms which have 

 been made known, nearly all are but partially pre- 

 served, only the hard parts, bones, teeth, shells, etc., 

 remaining, and the interpretation of these incom- 

 plete remains is often difficult, sometimes impossible 

 in the present state of knowledge. Exceptions to 

 this almost universal rule are so rare and occur so late 

 in geological time, as to be of little real assistance. 



(3) In Darwin's "Origin of Species" is a famous 

 chapter devoted to an examination of "the imperfec- 

 tion of the geological record," in which he points out 

 the accidental and haphazard way in which or- 

 ganisms have been fossilized and the great gaps which 

 occur in the history of life on the earth, so far as that 

 history has been discovered and deciphered. "I look 

 at the geological record as a history of the world im- 

 perfectly 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. 

 Each word of the slowly changing language, more or 



