76 SECTIONAL ADDRESSES. 
times vertebrates have inherited paired eyes; yet, as Professor Stockard 
has shown, if a little magnesium chloride is added to the sea-water in 
which the eggs of the fish Fundulus are developing, they will give rise to 
embryos with one median cyclopean eye! Nor is the suggestion any 
happier that the, so to speak, more deep-seated and fundamental 
characters are more constantly inherited than the trivial or superficial. 
A glance at organisms around us, or the slightest experimental trial, 
soon convinces us that the apparently least-important character may 
reappear as constantly as the most fundamental. But while an organ- 
ism may live without some trivial character, it can rarely do so when 
a fundamental character is absent, hence such incomplete individuals 
are seldom met in Nature. 
Yet undoubtedly some characters reappear without fail and others 
do not. If it is neither age nor importance, what is it that determines 
their inheritance? The answer is that for a character to reappear in 
the offspring it is essential that the germinal factors and the environ- 
mental conditions which co-operated in its formation in the ancestor 
should both be present. Inheritance depends on this condition being 
fulfilled. For all characters are of the nature of responses to environ- - 
ment ;? they are the products or results of the interaction between the 
factors of inheritance (germinal factors) and the surrounding 
conditions or stimuli. This power of response or reaction is no 
mysterious property of organisms—it is the effect produced, the dis- 
turbance brought about by the application of a stimulus. All the 
special properties and activities of living organisms ultimately depend 
on their metabolism, of which growth and reproduction are the chief 
manifestations. The course of metabolism, and, consequently, the 
development in the individual of a character, is moulded or conditioned 
by the environmental stimuli under which it takes place. On the 
other hand, the living substance, protoplasm, which is undergoing 
metabolism is the material basis of the organism. It has a specific 
composition and structure peculiar to the particular kind of organism 
concerned, and this is handed on to the offspring in the germ-cells from 
which starts the new generation. The inheritance of a character is due, 
then, not only to the actual transmission or transference of this specific 
“germ-plasm’ containing the same factors of inheritance (germinal 
factors) as those from which the parent developed, but also to this 
factorial complex developing under the same conditions (environmental 
stimuli), as those under which the parent developed. Any alteration 
either in the effective environmental stimuli or the germinal factors 
will produce a new result, will give rise to a new character, will cause 
the old character to appear no longer. 
Now what is actually transmitted from one generation to the next 
is the complex of germinal factors. Hence we should carefully dis- 
tinguish between transmission and inheritance. Much of the endless 
2 In a letter to Nature Sir Ray Lankester long ago drew attention to the 
importance of this consideration when discussing inheritance. He also pointed 
out that Lamarck’s first law, that a new stimulus alters the characters of an 
organism, contradicts his second law, that the effects of previous stimuli are 
fixed by inheritance. (Nature, vol, li, 1894,) 
