lOO YLVTJO^, Land Birds of New Zealand. [5th^"jan 



the air without making several preliminary hops ; as well as 

 Glaucopis, Sphcnceacus, and Prostheniadera, all of which are 

 feeble fiyers. x'\lso there is no reason for supposing that Ocy- 

 dromus, Strtngops, and Apteryx have any periodical periods of 

 semi-starvation, for all of them are as fat in the winter as in the 

 summer. Again, the Parrakeets of Antipodes and Auckland 

 Islands are as large as and as well fed as those of New Zealand, 

 although they have degenerated in the power of flight. And, 

 lastly, as the Moas were vegetable feeders, their food must, in a 

 climate like that of New Zealand, have been independent of the 

 season of the year. Consequently the hypothesis of the necessity 

 for periods of semi-starvation breaks down. Indeed, if a bird 

 was perishing from starvation wings would be useful to enable 

 it to search more ground and would be preserved by natural 

 selection. 



After this it seems hardly necessary to inquire whether the 

 supposed law of compensation of growth is a true one. What 

 evidence is there for supposing that in a time of semi-starvation 

 an organ which is not used suffers more than one which is used ? 

 I cannot find that anyone has, as yet, tried to produce any 

 evidence for or against it ; it is always taken for granted. The 

 only person who has discussed the subject at all is, so far as I 

 know, the late Mr. Herbert Spencer. In the second edition of 

 his " Principles of Biology " (vol. i., p. 328), he says that " it is a 

 general law of nutrition that when there is a deficiency of food 

 the non-essential organs suffer more than the essential ones, 

 and the unlikeness of proportion hence arising constitute 

 unlikeness of structure." But I cannot find that he gives any 

 evidence for this so-called general law, and his only attempt to 

 establish it is by a misleading analogy between a human society 

 and a living organism ; the labour and capital of the one being 

 supposed to represent the food supply of the other. This is an 

 argument which will not satisfy any scientific man. 



The thyroid and thymus glands are considered to be of little 

 or no use to the adult man. Do these glands suffer more than 

 other organs in periods of semi-starvation ? And in those tribes, 

 like the Australian blacks, which inhabit desert regions, and 

 are constantly suffering from want of food, have the glands 

 with them degenerated more than in other tribes ? This would 

 be a test case, but I have never heard that the facts support the 

 hypothesis. 



The evidence from New Zealand is, therefore, to the effect 

 that degeneration is not primarily due to natural selection either 

 in the ordinary way or through a supposed law of compensation 

 of growth. Nor can it be due to panmixia. The only explana- 

 tion left is that degeneration is due to disuse-inheritance ; and 

 as these variations clearly come under the head of acquired 

 characters, we seem to have in degradation a proof that these 

 characters may sometimes be transmitted from one generation 

 to another. Disuse we know to be a true cause of degeneration 



