258 OUTLINES OF EVOLUTIONARY BIOLOGY 



vestigial structures. A characteristic feature of oceanic islands 

 is the presence on them of birds which have more or less lost the 

 power of flight. Such were the dodo of Mauritius, the solitaire 

 of Rodriguez, and the gigantic moas of New Zealand. All these 

 forms are now extinct, but we still find in New Zealand several 

 flightless birds surviving. One of the most interesting is the 

 kiwi or Apteryx (Fig. Ill), a moderate-sized bird of nocturnal 



habits, now rapidly be- 

 coming exterminated. 

 The whole body is covered 

 with coarse, hair - like 

 plumage and externally 

 shows no trace of wings. 

 There is, however, a 

 minute remnant of a 

 wing present on each 

 side, completely con- 

 cealed in the plumage 

 and entirely functionless 

 as an organ of flight. 

 Yet it still possesses the 

 pentadactyl skeleton, 

 though in a greatly 

 reduced condition (Fig. 

 112). It is said that 

 when the kiwi goes to 

 sleep it still endeavours 

 to tuck its long beak 

 under its wing after the 



FIG. 112. Skeleton of a Kiwi, showing the manner of other birds, 

 vestigial Wing Bones, behind which a j th ti fc mo t 

 piece of Black Paper has been placed, 



x i. (From a photograph.) which the -kiwis are per- 



haps related, even the 



last vestiges of the wings seem to have disappeared, for amongst 

 the enormous quantities of the remains of these gigantic birds 

 which occur in New Zealand no wing bones have ever been found. 

 There is very strong reason to believe that the remote ancestors 

 of existing vertebrates possessed an additional pair of eyes on 

 the top of the head, behind the still existing lateral eyes. 

 Traces of this second pair the pineal or parietal eyes are yet 

 to be found in lampreys and lizards, and especially in that 



