THE EARLIEST KNOWN VERTEBRATES 19 



might be persuaded to yield a satisfactory an- 

 swer. The most direct way has been that of 

 tracing back the history of animal life by means 

 of fossil remains, but beyond a certain point 

 this method cannot go, since, for reasons stated 

 in various places in these pages, the soft 

 bodies of primitive animals are not preserved. 

 To supplement this work, the embryologist has 

 studied the early stages of animals, as their de- 

 velopment throws a side-light on their past 

 history. And, finally, there is the study of the 

 varied forms of invertebrates, some of which 

 have proved to be like vertebrates in part of 

 their structure, while others have been revealed 

 as vertebrates in disguise. So far these various 

 methods have yielded various answers, or the 

 replies, like those of the Delphic Oracle, have 

 been variously interpreted so that vertebrates 

 are considered by some to have descended from 

 the worms, while others have found their begin- 

 nings in some animal allied to the King Crab. 

 Every student of genealogy knows only too 

 well how difficult a matter it is to trace a fam- 

 ily pedigree back a few centuries, how soon the 

 family names become changed, the line of de- 



