364 JOURNAL OF SCIENCE. 
judging, from want of data on which to go. Thus in a flock of 
antelopes or similar animals, any individual increase of running 
powers must be looked upon as a favourable variation, since it enables 
the animals to flee more rapidly from their numerous enemies, but 
we do not know whether it may not be correlated with some 
corresponding defect. 
And here I may draw your attention to a great principle which 
is of universal application, which might be termed a principle of 
compensation or balance, but which is probably simply due to the 
limited power of development possessed by all individuals or groups 
of individuals. It is an almost invariable rule in Nature that if one 
part of an organism is greatly developed, it is usually accompanied by 
defective development of some other part. The most manifest 
examples which suggest themselves occur among men and domestic 
animals. If aman’s muscles are abnormally developed, we seldom 
find that he exhibits high brain power. Conversely if the intellectual 
development has been carried to extremes, the physical frame is 
usually only of average or less than average development. Among 
our domestic animals, such as the dog, we see the same general 
principle. The greyhound has his hind limbs enormously developed, 
and excels all other dogs in speed, but his brain is relatively very 
small, and the fore part of the body is very slenderly constructed. 
In the bulldog the jaws, neck, and fore-quarters generally are out of 
all proportion to the weak hind-legs, and the intelligence is very low. 
3ut in the poodle we have a dog uf comparatively feeble physical 
endowments, but the brain power is probably greater than in any 
other breed. Such examples might be multiplied ad nauseam, but let 
me now show the application of the same principle in some common 
lants. 
. Take the leaves of the Clianthus and the common Pea,* both 
belonging to the same natural order. The former has a tolerably firm 
stem, and its leaves are made up of a large number of leaflets with a 
pair of small stipules at the base. The Pea has given up the erect 
habit of stem if it ever had it, or perhaps originally it only trailed on 
the ground as chickweed does yet, but at any rate it has acquired a 
climbing habit. By doing this it dispenses with the production of a 
large amount of woody tissue, but it has to develop climbing organs 
to enable its leaves and flowers to obtain sunlight. These climbing 
organs it has produced at the expense of the major portions of its 
leaves, and now it has had to develop the stipules to act as leaves. 
You will notice the Pea has got three pairs of leaves and an odd one, 
but having turned two pairs and the odd one into tendrils, it has to 
depend on its stipules, which are primarily protecting organs, for 
part of the work which the leaflets would otherwise accomplish. 
Compare both of these with the leaf of a bean and you will see how - 
the same organ may undergo varied modifications according to its 
functions, and how the division of labour causes this principle of 
compensation to take effect. 
Again, here are flowers of Violets, Fuchsia, and Clematis. The 
first has on its stem two very minute scale-like bracts, then come five 
green sepals which are manifestly covering organs for the bud and 
* The lecture was illustrated by examples of the various plants referred to, 
which were placed in the hands of the audience, 
