66(> On Embryos iuul Nt'sflinys o/Centropus sinensis. 



■withstanding their late appearance and degenerate character, 

 the trichoptilcs appertaining to them appear at the same 

 time as, and are qnitc indistinguishable from, the others. 

 The arrangement of the triehoptiles is then prophetic of the 

 adult pterylosis, at least so far as the dorsal surface is con- 

 cerned, and a combination of the diagrams of the dorsal 

 view of the nestling of Stage 2, and of the ventral view of 

 Stage 3, fig. 5, will represent nearly exactly the adult ptery- 

 losis. The almost total absence of triehoptiles from the ventral 

 surface I would explain thus : — The embryo lies in the e;°^^ in 

 a strongly curved position, the dorsal side being the convex 

 surface, the ventral side the concave ; further, the curve is 

 so circumscribed that almost every part of the ventral sur- 

 face is in close contact with another part, and it is difficult 

 to see where room could be found for a dense mane of 

 triehoptiles such as is found on the dorsal surface, hence 

 must occur a retardation in the outward growth of these 

 structures along the area later occupied by the pt. ventralis. 

 But when the young bird hatches out, it lies or moves about 

 in the nest on its chest and stomach, subjecting these parts 

 to a considerable amount of friction ; and as I have already 

 shown that the dorsal triehoptiles become much worn though 

 subjected to much less friction, it is perhaps not unfair to 

 conclude that ventral triehoptiles will not be developed to 

 any extent if they are liable to be worn away on or soon 

 after their first appearance. Still, this is the merest specula- 

 tion, since I am unable even to hazard an opinion as to the 

 fimction of the triehoptiles : the nestling is certainly not 

 rendered inconspicuous by them, and as, moreover, it is con- 

 cealed in a deep nest, invariably built in dense undergrowth, 

 it is presumably independent of such protective devices ; and 

 still more unlikely is it, that the young of so highly spe- 

 cialized a group of birds as the Cuckoos should retain the 

 primitive body-clothing, and this quite ajiart from the fact 

 that both the distribution and structure of these triehoptiles 

 point the way to deductions of an opposite nature. 



The pterylosis of the adult Centropus sinensis differs in 

 one or two details from that of C. celebensis as described bv 



