BIRD-NOTES 65 



woven " lalang " grass (Imperata cylindrica) ; it is 

 placed on the ground, and is well hidden amongst the 

 tall rank grass which furnishes the bird with its build- 

 ing material. The embryos, when nearly ready for 

 hatching out, and the young nestlings present a most 

 peculiar appearance, for they are clothed on the dorsal 

 surface with a mane of long white hairs which affords 

 a striking contrast to the inky-black skin ; the ventral 

 surface is naked, and on the chin and belly the skin 

 is whitish. These hairs in reality are the immensely 

 prolonged tips of the feather-sheaths, the feathers being 

 still incompletely developed and quite hidden under 

 the skin. Since these structures are not true hairs it 

 is better to apply to them the name of " trichoptiles." 

 In the nearly ripe embryo the trichoptiles are very 

 long and are directed backwards in a flowing mane, 

 but a few days after hatching out the mane becomes 

 very rumpled, and the tips of the trichoptiles are 

 broken off, no doubt as a result of the movements 

 of the young birds in their nest and of the brooding 

 of the mother-bird. The bodies of adult birds are not 

 uniformly clothed with feathers, even though at first 

 sight they may appear to be, but the feathers grow 

 in certain tracts, known as " pterylae," and the bare 

 unclothed spaces are known as "apteria." The shape 

 and arrangement of the pterylae and apteria are of 

 great importance for purposes of classification. Seeing 

 that the trichoptiles are merely the elongated tips of 

 the sheaths which enclose the definitive feathers, it 

 might be supposed that their distribution over the 

 body of the embryo and nestling would be strictly 

 prophetic of the arrangement of the feathers of the 

 adult bird; but this is not so, for the trichoptiles are 



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