EVIDENCES OF EVOLUTION 55 



general idea of one organ leading on to an- 

 other is suggestive. It is consistent with our 

 general conception of development that 

 each stage supplies the necessary condition 

 for the next; it helps us to understand more 

 clearly how new structures, too incipient to 

 be functional, and old structures, too transi- 

 tory to be of direct use, may persist; in short, 

 it makes the process both of development 

 and of evolution more intelligible. But to 

 the idea of the architectural utility of the 

 notochord as a piece of scaffolding, we must 

 add, unless the recapitulation is simply 

 metaphorical, the idea that the notochord is 

 laid down to-day in the development of a 

 higher Vertebrate because of a continuity of 

 germinal material since the days of the an- 

 cestral forms which had no backbone at all. 

 It must be admitted that the recapitulation 

 doctrine has been often stated in somewhat 

 crude and exaggerated form, so that many 

 saving-clauses are necessary. The human 

 embryo is never like a little fish or a little 

 reptile; the resemblance is between embry- 

 onic stages. The recapitulation is general, 

 not exact; there is often abbreviation and a 

 masking of the old by the new. On the one 

 hand, old-fashioned features may drop out, 

 having no significance either in embryonic, 

 larval or adult life; on the other hand, many 



