PRELIMINARY DISCOURSE

an enquiry into the causes of life, of physical and moral sensitiveness, and, in short, of the lofty functions which he possesses.

It was first necessary to try to acquire knowledge of the organisation of the other animals. It was necessary to consider the differences which exist among them in this respect, as well as the relationships which are found between their special functions and the organisation with which they are endowed.

These different objects should have been compared with one another and with what is known of man. An examination should have been made of the progression which is disclosed in the complexity of organisation from the simplest animal up to man, where it is the most complex and perfect.

The progression should also have been noted in the successive acquisition of the different special organs, and consequently of as many new functions as of new organs obtained. It might then have been perceived how needs, at first absent and afterwards gradually increasing in number, have brought about an inclination towards the actions appropriate to their satisfaction; how actions becoming habitual and energetic have occasioned the development of the organs which execute them; how the force which stimulates organic movements can in the most imperfect animals exist outside of them and yet animate them; how that force has been subsequently transported and fixed in the animal itself; and, finally, how it has become the source of sensibility, and last of all of acts of intelligence.

If this method had been followed, feeling would certainly not have been looked on as the general and immediate cause of organic movements.

It would never have been said that life is a consequence of movements executed by virtue of sensations received by various organs or otherwise; nor that all vital movements are brought about by impressions received by sensitive parts (Rapport du physique et du moral de l’homme, pp. 38 to 39, and 85).

This cause would appear to be justified up to a certain point in the most perfect animals, but if it held good with regard to all bodies which enjoy life, they would all possess the faculty of feeling.

It could hardly be shown that this is the case in plants; it could hardly even be proved that it is the case in all known animals.

The supposition of such a general cause does not seem to me justified by the real methods of nature.

When constituting life, she had no power to endow with that faculty the imperfect animals of the earlier classes of the animal kingdom.

With regard to living bodies, it is no longer possible to doubt that nature has done everything little by little and successively.

12 Hence, among the various subjects which I intend to discuss in the present work, I shall endeavour to make clear by the citation of recognised facts that nature, while ever increasing the complexity of animal organisation, has created in order the different special organs, as also the functions which the animals possess.

The belief has long been held that there exists a sort of scale or graduated chain among living bodies. Bonnet has developed this view; but he did not prove it by facts derived from their organisa- tion; yet this was necessary especially with regard to animals. He was unable to prove it, since at the time when he lived the means did not exist.

In the study of all classes of animals there are many other things to be seen besides the animal complexity. Among the subjects of greatest importance in framing a rational philosophy are the effect of the environment in the creation of new needs; the effect of the needs in giving rise to actions, and of repeated actions in creating habits and inclinations; the results of increased or diminished use of any organ, and the means adopted by nature to maintain and to perfect all that has been acquired in organisation.

But this study of animals, especially of the least perfect animals, was long neglected; since no suspicion existed of the great interest which they exhibit. Moreover, what has been started in this respect is still so new that we may anticipate much more light from its further development. When the study of natural history was actually begun, and naturalists inquired into both kingdoms, those who devoted their researches to the animal kingdom studied chiefly the vertebrate animals, that is to say mammals, birds, reptiles and, lastly, fishes. In these classes of animals the species are in general larger, and have their parts and functions better developed and more easily ascertainable than the species of invertebrate animals. Their study, therefore, seemed to present more of interest.

In fact the majority of invertebrate animals are extremely small, their functions are limited, and their organs much more remote from those of man than is the case of the more perfect animals. As a result, they have been to some extent despised by the vulgar, and down to our own time have only realised a very moderate amount of interest on the part of most naturalists.

We are beginning, however, to get over a prejudice so harmful to the progress of knowledge. During the few years that these singular animals have been closely examined, we have been compelled to recognise that the study of them is highly interesting to the naturalist and philosopher, because it sheds light, that could scarcely be other- wise obtained, on a number of problems in natural history and animal physics. It has been my duty in the Natural History Museum to