Vol. IV. 

 1905 



1 H\]TTOH, Land Birds of New Zealand. lOI 



in the individual — it is the only true cause that we know ; and 

 everyone will allow that it is the starting point, or originating 

 cause, of degeneration. The difficulty is to explain how varia- 

 tions, in an organ, caused by disuse, become progressive. That 

 is, how do they accumulate generation after generation until at 

 last the whole organ disappears ? Or in other words, how does 

 disuse give rise to disuse-inheritance ? 



It has been suggested that disuse-inheritance is due to a reverse 

 process of development — a going back through the process on 

 which an organ was developed. This is, however, no explana- 

 tion, even if it were a true account of the facts. But in the case 

 of the wings of birds it is evidently incorrect ; for if true the 

 fingers of the wing would become free before the wing was much 

 reduced ; whereas we see in the Kiwi, and other struthious 

 birds, that the fingers are lost without becoming free. 



Let us try for another explanation. We know that habits 

 are sometimes inherited. This must mean that some alterations 

 in the structure of the brain in one individual are transmitted 

 to its descendants. These inherited habits, when developed by 

 natural selection, become instincts. This is the only possible 

 explanation of the origin of instincts which are so strongly 

 developed in birds. These instincts are due to unconscious 

 memory, just as are the habits from which they spring. But 

 it is difficult, if not impossible, to draw a line between acknow- 

 ledged instincts and the development of the various tissues of 

 the body. If breathing is an instinct, so also is the beating of 

 the heart, so also is reproduction. And we cannot deny that 

 the process of growth is also directed by instinct. For if re- 

 production is an instinct, then the production of two individuals 

 from one is due to instinct ; but if the two cells adhere together 

 instead of forming two distinct individuals, we must allow that 

 this is also an instinct. In fact, all cell division must be due 

 to instinct — that is, to the autonomous working of unconscious 

 memory. This is Professor Hering's theory of heredity being 

 due to unconscious memory. The growth of one cell on another 

 recalls some action that took place when two similar cells were 

 similarly placed in a former generation. He says: — " When the 

 first germ divided it bequeathed its properties to its descendants ; 

 the immediate descendants added new properties, and every 

 new germ reproduced to a great extent the modi operandi of 

 its ancestors. Each generation endows its germ with some small 

 property which has been acquired during life, and this is added 

 to the total legacy of the race. Thus every living being of the 

 present day is the product of the unconscious memory of 

 organized matter." 



Now this theory also gives us an explanation of disuse- 

 inheritance. For when an organ is not used the unconscious 

 memories of the part are weakened, and in the next generation 

 the organ is reproduced in a more feeble condition, until at last 

 it is not reproduced at all, the memory of the operation having 



