154 THE INFANCY OF ANIMALS 



the feather be removed from the body, it is almost im- 

 possible to distinguish between main shaft and after- 

 shaft. 



From this it has always been argued that the large 

 aftershaft is an ancestral feature which has survived. 

 This may be so. But if it be, it is difficult to reconcile 

 what obtains among the tinamous, on the one hand, 

 and the nestlings of the ostrich tribe on the other. For 

 in the emu and cassowary the aftershaft is almost 

 obsolete, in the nestling ostrich it is large, but absent in 

 the adult ; in the tinamou it is obsolete in the adult, 

 very large in the nestling ! So far no one has been able 

 to interpret these contradictory facts. 



In another point, however, the cassowaries do conform 

 to the rule that the characters displayed by the nestling 

 to-day are features which belonged to the adults of the 

 past ; and this in the matter of those extraordinary 

 quills which stick out from each wing in the adult. These 

 seem to be neither useful nor ornamental, and even 

 their true nature was mistaken until it was made clear 

 by the revelations of the nestling, or rather the bird 

 in its later " juvenile " plumage. Examining a series of 

 these I found that these quiUs were here represented by 

 relatively normal feathers — that is to say by feathers 

 which displayed a hollow quill, surmounted by a shaft 

 bearing a double row of barbs. 



Sooner or later, to make a long story short, the shaft 

 bearing the vane sloughed off, leaving only the quiU, 

 which then rapidly increases in length and thickness, 

 ultimately forming the rather crooked spike already 

 referred to. Not the least curious thing about this trans- 

 formation is that in the Apteryx the quills throughout 

 life are of the type seen in the immature cassowary. 



