ADJUSTMENT, DIRECT AND INDIRECT 



from the pterodactyl, why do the struthious 

 birds so strongly resemble a totally different rep- 

 tile ? If all birds started from a dinosaurus, why 

 do the carinate 'birds so strongly resemble the 

 pterodactyl? If we try to split the difference, 

 and say that the carinate birds started from the 

 pterodactyl, while the struthious birds started 

 from the dinosaurus, the difficulty is immensely 

 increased. For then the question arises, how 

 could the struthious and the carinate birds, start- 

 ing from such different points, have come to 

 resemble each other so strongly ? 



Mr. Mivart is careful to state that these zo- 

 ological cross - relations do not constitute an 

 obstacle to the theory of evolution. They are 

 difficulties only on the theory that organic evo- 

 lution has been solely caused by the natural 

 selection of fortuitous variations. To make this 

 more clear, let us provisionally accept one of 

 each of the pairs of alternatives offered by the 

 two cases just described. Let us agree, with 

 Professor Haeckel, that all the monodelphian 

 mammals have come from one didelphian ; and 

 let us agree, with Professor Huxley, that the 

 kinship between birds and reptiles is closest in 

 the case of the struthious birds and the dinosau- 

 rians. Now we are obliged to maintain that the 

 original monodelphian branched off into a dozen 

 or more forms, of which six or seven happen to 

 agree remarkably, in general appearance and in 



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