COSMIC PHILOSOPHY 



what resembles a lizard with a bird's beak. Em- 

 bryology shows that the three classes are diver- 

 gent offshoots from an amphibious or batra- 

 choid ancestor ; but the birds and the reptiles 

 resemble each other much more closely than 

 either resembles the mammalia, so that Profes- 

 sor Huxley joins them together in the super- 

 class or province of sauroids. So far all is plain ; 

 but when we inquire by what forms the birds 

 and reptiles are linked most closely together, 

 we are met by a difficulty. Birds are divided 

 into two sub-classes : the ostrich, cassowary, 

 emeu, dinornis, etc., are grouped together as 

 struthious birds, while all other existing forms 

 belong to the sub-class of carinate birds. Now 

 until quite lately it was supposed that all birds 

 were descended from an extinct reptilian form 

 like that ancient reptile, the flying pterodactyl. 

 For the resemblances in structure between the 

 pterodactyls and the carinate birds are striking 

 enough to have suggested an immediate com- 

 munity of origin. Nevertheless, within the past 

 seven years, a much stronger case has been 

 made out in favour of the descent of the stru- 

 thious birds from large reptilian forms akin to 

 the dinosauria, — of which extinct order the 

 member most commonly known is the gigantic 

 iguanodon. Now here, says Mr. Mivart, is a 

 dilemma just like the one which confronted us 

 in the case of mammals. If all birds started 

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