October 3, 1901] 



NA TURE 



367 



he treat established genera gently. No doubt there are types of 

 animals of whose structure we are woefully ignorant ; no doubt 

 we need to know their internal anatomy in great detail. So 

 welcome to the zootomist in this new century, and may he 

 invent fewer long names for new organs. No doubt there are 

 groups of whose relationships we know little, and which have 

 been buffeted about from one class to another in a bewildering 

 way. We need to have their places fixed. So welcome to the 

 comparative anatomist and the embryologist, and may their 

 judgment as to the relative value of the criteria of homology 

 grow clearer. No doubt our knowledge of inheritance and 

 development will be immensely advanced by the further study 

 of centrosomes, asters and chromosomes. Welcome, therefore, 

 to the cytologist, and may he learn to distinguish coagulation 

 products and plasmolytic changes from natural structures. All 

 these subjects have victories in store for them in the new 

 century. To neglect them is to neglect the foundations of 

 zoology. 



But the coming century will, I predict, see a change in the 

 methods of studying many of these subjects. In systematic 

 zoology fine distinctions will no longer be expressed by the 

 rough language of adjectives, but quantitatively, as a result of 

 measurement. There is every reason to expect, indeed, that 

 the future systematic work will look less like a dictionary and 

 more like a table of logarithms. Our system of nomenclature, 

 meanwhile, will probably break down from its own weight. 

 Now that the binomial system of nomenclature has been replaced 

 by a trinomial, there is no reason why we should not have a 

 quadrinomial nomenclature or even worse. It seems as if the 

 Linn^an system of nomenclature is doomed. What will take 

 its place can hardly be predicted. The new system should 

 recognise the facts of place-modes and colour-varieties. We 

 might establish certain categories of variation such as those of 

 geographical regions, of habitat, of colour. A decimal system 

 of numbers might be applied to the parts of the country or the 

 kinds of habitat and the proper number might take the place of 

 the varietal or subvarietal name. Thus the north-eastern skunk 

 might be designated Mephitis mephitica 74, and the south- 

 eastern skunk Mephitis mephitica 75 (adopting the Dewey 

 system of numerals). The Maine skunk would then be 741, 

 that of New York 747, and so on. This much for a suggestion. 



So likewise for the morphologist the coming century will 

 bring new aims and new methods. No longer will the construc- 

 tion of phylogenetic trees be the chief end of his studies, but a 

 broad understanding of the form producing and the form main- 

 taining processes. The morphologist will more and more con- 

 sider experiment a legitimate method for him. The experimental 

 method will, I take it, be extended especially to the details of 

 cytology, and here cytology will make some of its greatest 

 advances. 



Not only will the old subjects be studied by new methods, but 

 we have every reason to believe that new subsciences will arise 

 during the twentieth century as they arose during the nineteenth. 

 Of course we cannot forecast all of these unborn sciences, as 

 cytology .ind neurology could hardly have been forecast at the 

 beginning of the nineteenth century. But we can see the be- 

 ginnings of what are doubtless to be distinct sciences. Thus 

 comparative physiology is still in its infancy, and is as yet hardly 

 worthy of the name of a science ; there is no question that this 

 will develop in the coming decades. Animal behaviour has long 

 been treated in a desultory way, and many treatises on the sub- 

 ject are rather contributions to folk-lore than to science. But we 

 are beginning to see a new era — an era of precise, critical and 

 objective observation and record of the instincts and reactions 

 of animals. One day we shall reach the stage of comparative 

 studies and shall have a science of the ontogeny of animal in- 

 stincts. This will have the same importance for an interpret- 

 ation of human behaviour that comparative anatomy and embry- 

 ology have for human structure. 



Prominent among the advances of the century will be the 

 ability to control biological processes. We shall know the fac- 

 tors that determine the rate of growth and the size of an animal, 

 the direction and sequence of cell-divisions, the colour, sex and 

 details of form of a species. The direction of ontogeny and of 

 phylogeny will be to a greater or less extent under our control. 



The study of animals in relation to their environment, long 

 the pastime of country gentlemen of leisure, will become a 

 science. Some day we shall be able to .say just what determines 

 an animal's presence at any place ; and, more than that, we 

 shall be able to account for the fauna, the sum total of animal 



NO. 1666, VOL. 64] 



life of any locality, and to trace the history of that fauna. This 

 is at least one of the aims of animal ecology. It is a 

 reproach to zoology that the subject of animal ecology 

 should lag so far behind that of plant ecology. When zoo- 

 logists fully awaken to a realisation of what a fallow 

 field lies here this reproach will quickly be wiped out. 

 As it is we have a notion that the factors determining the occur- 

 rence of an animal or of a fauna are too complicated to be un- 

 rjivelled. As a matter of fact the factors are often quite simple. 

 Let me illustrate this by some studies I have made this summer 

 on the Cold Spring Beach. This beach is a spit of sand 2000 

 feet long and 50 to 75 feet broad, running from the western 

 mainland into the harbour and ending in a point that is being 

 made several feet a year through the cooperation of wave, tide, 

 and a silt-transporting creek of fresh water. On the outer 

 harbour side is a broad, gradually sloping sandy and gravelly 

 beach, covered by high tide, and devoid of living vegetation. 

 Above that is a narrow zone — the middle beach — covered with 

 the debris of storms, supporting a few annual plants, and 

 bounded above by a storm-cut bluff. Above is the upper beach, 

 covered with a perennial, sand-loving vegetation. On the 

 lower beach the zonal distribution of animals is striking. Just 

 above the water are found the scavenger mud-snails, and, 

 further up, a crowd of Thysanura — small insects that rise to the 

 surface of the water when the tide comes in. These find a 

 living on the finer debris or silt that settles on the pebbles 

 during the high tides. In this zone also Limulus lays its eggs 

 in the sand, and its nests are crowded with nematodes that feed 

 on the eggs. During the breeding season scores of the female 

 Limulus die here, and their carcasses determine a complex 

 fauna. First, carrion beetles (Necrophorus) and the flesh fly 

 live on the dead bodies ; then the robber flies and tiger-beetles 

 are here to feed on this fauna, and, finally, numerous swallows 

 course back and forth, gleaning from this rich field. At the 

 upper edge of the lower beach is a band of debris dropped at 

 slack water and consisting especially of shreds of Ulva and 

 many drowned insects, especially beetles. At this zone or just 

 above, under the drier but more abundant wreckage of the last 

 storm, occur numerous Amphipoda of the genera Orchestia and 

 Talorchestia. Associated with these marine creatures are 

 numerous red ants, sand-coloured spiders and rove-beetles. 

 The amphipods feed on the decaying sea-weed. The ants 

 are here looking chiefly for the drowned insects. Their 

 nests are further up on the middle beach, but the workers travel 

 to the edge of the high tide to bring away their booty. 

 The rove-beetles are general scavengers. The spiders, which 

 are mostly of the jumping sort (of the family Attidse), feed on 

 the active insects and amphipods. At a higher zone and above 

 all but the storm-driven tides one finds the nests of the ants, 

 especially under logs, certain predaceous beetles and the 

 xerophilous grasshoppers and crickets. Finally, on the plant- 

 covered upper beach one finds characteristic leaf-eating beetles, 

 grasshoppers and carnivorous insects. Now all this seems com- 

 monplace enough and not especially instructive, and yet if you 

 go to the shore of Lake Michigan you will find on a similar 

 beach closely similar, if not identical, forms (excepting the beach 

 fleas and the horse-shoe crabs) ; you will find similar ants, 

 spiders, rove-beetles, tiger-beetles and sand grasshoppers. This 

 fact alone shows the greater importance of habitat over geographi- 

 cal region in determining the assemblage of animals that occurs in 

 anyone place. It may be predicted that studies on the relation 

 of animals to their habitat will multiply, that they will become 

 comparative and that the science of animal ecology will become 

 recognised as no less worthy and no less scientific than the 

 science of morphology. 



Studies on the origin of species were far from being unknown 

 in the nineteenth century, but they were for the most part frag- 

 mentary or speculative or narrow in view. The opinion that there 

 was one method of evolution seemed to hold sway. It seems to me 

 that the signs of the times indicate that we are about to enter upon 

 a thorough, many-sided, inductive study of this great problem, 

 and that there is a willingness to admit that evolution has ad- 

 vanced in many ways. The attempt, therefore, to explain all 

 specific peculiarities on the ground of natural selection, or on the 

 ground of self-adjustment, or on the ground of sport-preservation 

 through isolation we may expect equally to prove futile. All 

 these causes are no doubt real in some cases, but to exclude any 

 one or to deny that new causes may be found in the future is 

 equally dangerous and unscientific. 



It is often said that the factors of evolution are inheritance and 



