290 THE STRUCTURE AND LIFE OF BIRDS chap. 



its claw. But the most wonderful point of all is that 

 the three outermost primaries have their growth arrested 

 while the others advance in length ; later on they 

 grow to their full size. This can be well seen in the 

 series of young chickens in the hall at the South 

 Kensington Museum. And so the chicken, a thor- 

 oughly modernized relative of the archaic Hoatzin, 

 still retains this queer trace of its ancient life. 



The anatomy and habits of Hoatzin may help us to 

 understand what may have been the manner of life of 

 Archaeopteryx. Mr. Pycraft suggests that it used its 

 claws mainly during its infancy. May it not also have 

 had recourse to them when moulting ? A poor flyer 

 at best, and its leg-muscles possibly weak, it might 

 well, when bereft of some of its big feathers, or, 

 through an imperfect system of moulting, bereft of 

 all at once, appreciate fully the value of wing-claws, to 

 help it to climb out of the reach of reptile enemies. 



We will now pass on to a comparatively common- 

 place subject. As a rule a young bird differs in 

 plumage from a mature one. The cock bird as he 

 grows up often puts on fine plumes unknown to his 

 youth. If there is a difference in brightness between 

 the old birds and the young, it is always the latter 

 which are characterised by the more sober dress. 

 But beyond this it is impossible to find a rule that will 

 apply to all. When the cock is more conspicuous 

 than the hen, the young usually resemble the mother. 

 The young cock Blackbird, however, is easy to dis- 

 tinguish in the nest by his darker tint. In the Painted 

 Snipes and the few other species in which the female 

 bird is more gaudy than the male, it is the latter that 



