508 TRANSACTIONS OF SECTION D. 
The life of an organism, with all its experiments and doings, is its Ontogeny, 
which may therefore be called the subject of Evolution, but not a factor. Nor is 
Selection a primary and necessary factor, since, being destructive, it invents 
nothing. It accounts, for instance, for the composition of the present fauna, but 
has not made its components. A subtle scholastic insinuation lurks in the plain 
statement that by ruthless elimination a black flock of pigeons can be produced, 
even that thereby the individuals have been made black. (But of course the 
breeder has thereby not invented the black pigment.) 
There can be no evolution, progress, without response to stimulus, be this 
environmental or constitutional, i.e., depending upon the composition and the 
correlated working of the various parts within the organism. Natural selection 
has but to favour this plasticity, by cutting out the non-yielding material, and 
through inheritance the adaptive material will be brought to such a state of plas- 
ticity that it is ready to yield to the spur of the moment, and the foundation 
of the same new organs will thereby be laid, whenever the same necessity calls 
for them. Here is a dilemma. On the one hand the organism benefits from the 
ancestral experience, on the other there applies to it de Rosa’s law of the 
reduction of variability, which narrows the chances of change into fewer direc- 
tions. But in these few the changes will proceed all the quicker and farther. 
Thus progress is assured, even Hypertely, which may be rendered by ‘ over-doing 
a good thing.’ 
Progress really proceeds by mutations, spoken of before, orthogenesis, and it 
would take place without selection and without necessarily benefiting the 
organism. It would be mere presumption that the seven-gilled shark is worse 
off than its six- or five-gilled relations; or to imagine that the newt with double 
trunk-veins suffers from this arrangement, which morphologically is undoubtedly 
inferior to the unpaired, azygous, &c., modifications. The fact that newts exist 
is proof that they are efficient in their way. Such orthogenetic changes are as 
predictable in their results as the river which tends to shorten its course to the 
direct line from its head waters to the sea. That is the river’s entelechy and no 
more due to purpose or design than is the series of improvements from the many 
gill-bearing partitions of a shark to the fewer, and more highly finished comb- 
shaped gills of a Teleostean fish. 
The success of adaptation, as measured by the morphological grade of per- 
fection reached by an organ, seems to depend upon the phyletic age of the 
animal when it was first subjected to these ‘temptations.’ The younger the 
group, the higher is likely to be the perfection of an organic system, organ, or 
detail. This is not a platitude. The perfection attained does not depend 
merely upon the length of time available for the evolution of an organ. A 
recent Teleostean has had an infinitely longer time as a fish than a reptile, and 
this had a longer time than a mammal, and yet the same problem is solved in a 
neater, we might say in a more scientifically correct, way by a mammal than by 
a reptile, and the reptile in turn shows an advance in every detail in comparison 
with an amphibian, and so forth. 
A few examples will suffice :— 
The claws of reptiles and those of mammals; there are none in the amphi- 
bians, although some seem to want them badly, like the African frog Gampsos- 
teonyx, but its cat-like claws, instead of being horny sheaths, are made out of 
the sharpened phalangeal bones which perforate the skin. 
The simple contrivance of the rhinocerotic horn, introduced in Oligocene 
times, compared with the antlers of Miocene Cervicornia and these with the 
response made by the latest of Ruminants, the hollow-horned antelopes and 
cattle. The heel-joint; unless still generalised, it tends to become intertarsal 
(attempted in some Lizards, pronounced in some Dinosaurs and in the Birds) 
by fusion of the bones of the tarsus with those above and below, so that the 
tarsals act like epiphysial pads. Only in mammals epiphyses are universal. 
Tibia and fibula having their own, the pronounced joint is cruro-tarsal and all 
the tarsals could be used for a very compact, yet non-rigid arrangement. The 
advantage of a cap, not merely the introduction of a separate pad, is well 
recognised in engineering. 
Why is it that mammalian material can produce what is denied to the lower 
classes? In other words, why are there still lower and middle classes? Why 
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