Embryology. i o i 



chapter on Classification — we have seen that if each 

 species were created separately, no reason can be 

 assigned why they should all have been turned out 

 upon structural patterns so strongly suggestive of 

 hereditary descent with gradual modifications, or slow 

 divergence — the result being group subordinated to 

 group, with the most generalized (or least developed) 

 forms at the bottom, and the highest products of 

 organization at the top. And now we see — or shall 

 immediately see — that this consideration admits of 

 being greatly fortified by a study of the develop- 

 mental history of every individual organism. If it 

 would be an unaccountable fact that every separately 

 created species should have been created with close 

 structural resemblances to a certain limited number 

 of other species, less close resemblances to certain 

 further species, and so backwards ; assuredly it would 

 be a still more unaccountable fact that every indi- 

 vidual of every species should exhibit in its own 

 person a history of developmental change, every term 

 of which corresponds with the structural peculiarities 

 of its now extinct predecessors — and this in the exact 

 historical order of their succession in geological time 

 The more that we think about this antithesis between 

 the naturalistic and the non-naturalistic interpreta- 

 tions, the greater must we feel the contrast in respect 

 of rationality to become ; and, therefore, I need not 

 spend time by saying an}thing further upon the 

 antecedent standing of the two theories in this 

 respect. The evidence, then, which I am about to 

 adduce from the study of development in the life- 

 histories of individual organisms, will be regarded by 

 me as so much unquestionable evidence in favour of 



