306 THE RECAPITULATION THEORY 



welcome light on what was previously a great mor- 

 phological puzzle. 



We must now turn to another side of the ques- 

 tion. Although it is undoubtedly true that develop- 

 TneTTr~!s to be regarded as a recapitulation of 

 ancestral phases, and that the embryonic history 

 of an animal presents to us a record of the race- 

 history, yet it is also an undoubted fact, recognised 

 by all writers on embryology, that the record so 

 obtained is neither a complete nor a straightforward 

 one. It is indeed a history, but a history of which 

 entire chapters are lost, while in those that remain 

 many pages are misplaced and others are so blurred 

 as to be illegible ; words, sentences, or entire para- 

 graphs are omitted, and, worse still, alterations or 

 spurious additions have been freely introduced by 

 later hands, and at times so cunningly as to defy 

 detection. 



^ Very slight consideration will show that develop- 

 ment cannot in all cases be strictly a recapitulation 

 oT ancestral stages. It is well known that closely 

 allied animals may differ markedly in their mode 

 of development. The common frog is at first a 

 tadpole, breathing by gills, a stage which is entirely 

 omitted by the West Indian Hylodes. A crayfish, 

 a lobster, and a prawn are allied animals, yet they 

 leave the egg in totally different forms. Some 

 developmental stages, as the pupa condition of 

 insects, or the stage in the development of a dog- 

 fish in which the oesophagus is imperforate, cannot 

 possibly be ancestral stages. Or again, a chick 

 embryo of say the fourth day is clearly not an 



