PHYLOGENT OP THE PAL^OGNATH^ AND NEOGNATH^. 163 



the rhachis bears about 6 or 7 pairs of rami. The radii are slightly stouter, relatively. 

 As in Casuarius, fila are minute and rare. 



The nestling-down of Aptenjx (PI. XLV. fig. 6) is easily distinguishable from that 

 of the remaining Palceognatha;. Like that of Dromwus and Casuarius, it has a 

 well-developed shaft, but it differs from these in its greater length and in the very 

 numerous rami. From EJiea and Struthio it differs entirely, in that, in these, the 

 neossoptiles are umbelliform. 



The most striking feature perhaps of the nestling-plumage of Apfertjx is its great 

 length. In texture we appear to get three gradations. A. australis mantel li and 

 australis very closely resemble one another and differ from the remaining species in 

 that the feathers are coarser and slightly harsh to the touch. A. oiveni and A. haasti 

 stand at the other extreme and are peculiarly soft. Some individuals of A. australis, 

 however, seem to stand between the two. 



A. haasti is the most markedly distinct of all. The feathers clothing the head, neck, 

 and thighs are of a peculiarly downy character, recalling, in texture, the down-feathers 

 on the breast of tlie adult Duck. On the back and breast they are of a peculiar 

 "woolly" texture, resembling very strongly the intermediate plumage or pseudo- 

 definitive feathers, (mesophyles of Palmer), which follow the prepenn« in the Owls. 

 There is no trace of an aftershatt to these prepennae. 



The rami are closely set, very numerous (18 to 20 pairs), and moderately long. The 

 radii are relatively short, and have the appearance of being formed of a number of 

 short, laterally compressed joints, the dorsal and ventral angles of the anterior ends of 

 which are produced forwards to form a pair of minute lila. 



In the length of the shaft and the great number of the rami tlie prepenna of ylpteri/x 

 stands alone amongst the Pala^ognathw; moreover it is further peculiar in that it is not 

 produced beyond the most distal radii into long filaments. 



A peculiarly interesting feature of the prepemue, and of the first definitive feathers, 

 is that the latter do not thrust out the former, as they appear to do in all other known 

 birds. Exactly how this is avoided is a point for further investigation. I hope to be 

 able to explain this mystery shortly \ That this process of thrusting-out is avoided 

 can be still seen in a downy nestling of A. haastii in the Kothschild Collection. Here 

 the first definitive feathers are about halfway through the skin, and show no trace 

 whatever of a prepenna surraountmg the tips, as do the other Palm- and NeocjnatJm. 

 Furthermore, they are peculiar in that they are not invested by the sheath common to 

 all developing feathers. This appears to break away as soon as it reaches the surface 

 of the skin. 



' It may possibly turn out that this nestling-down plumage may represent preplumoe instead of prepennie : 

 this would account for their non-ejectment hy the teleoptiles. The fact that plumula; do not occur in the 

 adult is of no importance. Zander [loi] has described " pinsel-artig " down-feathers in the embryo Ukea, but 

 this is probably an error. 



