BIRDS OF OLD 67 



In succeeding generations the pelvic wings would be- 

 come more and more reduced. Having arisen from 

 among the surrounding scales, they had for a time vol- 

 planed through the air of early ages, a structure passive 

 and, as future centuries would show, of merely transi- 

 tory function. Yet they were of tremendous importance 

 in allowing the pectoral scales to develop, to become 

 feathers, and then to assume an importance which was 

 to make the class of birds supreme in the air. Yet the 

 function of the pelvic wings had been so passive and 

 negative that no special muscling had been necessary, 

 no increase or coalescence of bony tissue. Little by 

 little the line of feathers and their coverts sank into 

 insignificance and became lost among the body plum- 

 age. It affords an excellent example of what Professor 

 Henry F. Osborn would call the phylogenetic accelera- 

 tion of a character, followed by its gradual reduction. 



Millions of years after they were of use, the feathers of 

 the pelvic wing are still reproduced in embryo and 

 nestling. And for some unknown reason, Nature makes 

 each squab pass through this Tetrapteryx stage. The 

 line of feathers along the leg of the young bird repro- 

 duces in this diminutive, useless way the glory that once 

 was theirs. No fossil bird of the ages prior to Archceop- 

 teryx may come to light, but the memory of Tetrap- 

 teryx lingers in every dove-cote." 



Thus were scaly, creeping reptiles transformed into 

 feathered, flying birds. 



REFERENCES 



The first discovered specimen of Archceopteryx, Archce- 

 opteryx macrura, is in the British Museum, the second more 

 complete example is in the Royal Museum of Natural History, 

 Berlin. The largest collection of toothed birds, including the 

 types of Hesperornis, Ichthyornis and others, is in the Yale 



