YOUNG BIRDS AND RECORDS OF THE PAST 137 



together. And if we turn to the newly hatched chick, 

 or better still to the nearly ripe embryo, we shall find 

 that such is actually the case. And if we compare a 

 number of such tails of different species — gallinaceous 

 birds, ducks or swans, for example — we shall see that 

 these separate elements range in number from five to 

 ten ; therefrom we conclude that this pygostyle is a new 

 thing, relatively speaking ; that time was when the end 

 of the tail was made up of a number of separate bones, ^ 

 represented to-day by this pygostyle. 



The fossil archaeopteryx shows that this was actually 

 the case, the tail being extremely long, like that of a lizard. 

 But this is not its only peculiarity. The tail feathers, 

 it will be noticed, are attached in pairs aU the way down 

 from its base to its tip, a pair of feathers to each separate 

 vertebra, a plan differing entirely from that which obtains 

 in modern birds, wherein, as we have seen, these feathers 

 are arranged fan-wise about the pygostyle. 



At first sight these two types of tails seem to have 

 little in common : yet a little study of the matter will 

 end in the conviction that they are not only closely re- 

 lated, but that the one has been derived from the other. 

 The process by which the transformation has come about 

 is not difficult to follow. If one carefully studies the tail 

 of this ancient bird one can see how, if by some process 

 we could " telescope " these bones, compress them by 

 pressure at each end, till from cylinders they became 

 little more than discs of bone, we should at once reproduce 

 the characteristic fan-wise method of arrangement which 

 these feathers present in modern birds. Yet but for the 

 facts revealed by the examination of the pygostyle in the 

 "parson's nose," and of the earlier embryonic stages, I ven- 

 ture to think we should never have alighted on this solution. 



