Russel Wallace : Alfred Russell Wallace (sic)
[[p. 335]] The six lectures of which this volume consists treat of the relations of insects and plants, the habits of ants, and prehistoric archæology. They are well illustrated by numerous woodcuts, and are written in the clear and pleasing style which characterises all Sir John Lubbock's works.
The first lecture--On Flowers and Insects--gives an excellent account of some of the more interesting cases of the special adaptation of flowers for insect fertilization, but contains nothing that will be new to the readers of Nature. The next--On Plants and Insects--introduces us to a variety of interesting and less generally known relations between the insect and vegetable worlds, which serve to confirm in a striking manner the general axiom, that the minutest details in the structure of living things, are or have been of use to them. We learn now how much of what gives a special character to many plants--their hairy or woolly stems, their spines, their glutinosity, the hairy rings inside their flowers, their drooping habit or glossy surfaces--are all of use in various ways to keep off insects which would rob them of their honey or pollen without effecting fertilisation. Another relation here dwelt upon is that of the colouring of caterpillars in accordance with the plants they feed upon, and it is particularly instructive as showing how impossible it is to decide whether a creature is protected by its colour unless it is observed in its native haunts. Few objects are more beautiful, or more varied in colour and markings, than the caterpillars of our different species of hawk-moths. They are often adorned with the most exquisite violet, blue, or white markings on a green ground, and sometimes also with ocellated spots of brilliant colours, yet in most cases these are so arranged and balanced as to harmonise with the general tints of foliage and flowers of the food plant and thus render the insect quite inconspicuous at a little distance. In addition to the excellent woodcuts of caterpillars which illustrate this part of the work there is a coloured frontispiece which appears to have been added as an afterthought, for not only is there no reference to it in the text, but not even the names of the insects are given on the plate itself.
The next two lectures--On the Habits of Ants--give an excellent summary of those interesting researches by which Sir John Lubbock has added so much to our knowledge of these insects. Especially curious are the illustrations of the stupidity of some ants. One species is such a confirmed slave-owner that it dies of hunger if not fed by its slaves--a fact recorded by Huber and confirmed by our modern observer. Even more striking as an example of want of intellect is the experiment recorded at p. 81, where some ants went round a distance of ten feet to get at honey rather than jump down about one-third of an inch; and although they tried to reach this small height, from a little heap of earth to the glass on which the honey was placed, and could even touch it with their antennæ, yet they had not sense enough to pile up the earth a little higher but gave it up in despair and went round by the paper bridge ten feet in length!
Numerous experiments show that some sense analogous to smell, rather than vision, guides ants to their food, and thus no actual power of communication from one ant to another is needed to account for the numbers that follow when one has found out a store. Some very ingenious experiments prove, however, that an actual communication does exist when larvæ are concerned, and that one ant is able to tell its fellows whether there are few or many larvæ to be attended to. The experiments as to the effects of coloured light on ants are interesting, showing [[p. 336]] that they have a great dislike to violet light however obscure, and a preference for dark green and red; but we can hardly tell whether this effect depends on any visual perception, or on a general sense of discomfort in the one case and pleasure in the other analogous to the effects of heat and cold upon ourselves.
The last two lectures give a clear and condensed summary of the present state of our knowledge as to prehistoric man, and are well worthy of study by those who may be inclined to doubt the value of the conclusions arrived at by the new science of Prehistoric Archæology. There is here of course nothing but what is well known to all who have paid attention to the subject. It is, however, interesting to note how sharp and striking the contrast between the Palæolithic and Neolithic ages appears, when their characteristic features are briefly summed up side by side as we here find them. Whether we consider the tools, weapons, and other works of art, the character of the contemporary animals, the physical geography of the country, or the distribution of man himself, we cannot but be impressed with the profound chasm, which in Europe at least, separated the Palæolithic from the Neolithic man. And as, since the glacial epoch passed away we have no evidence of any physical changes calculated to produce such a chasm, it seems natural to suppose that it was the result of the cold period itself, and that, as many geologists now maintain, Palæolithic man lived before the glacial epoch and during interglacial mild periods, while Neolithic man made his first appearance only when the ice-age had finally passed away. On any other theory we have no adequate cause adduced for a discontinuity so vast in its proportions and extending over so wide an area.
A. R. W.