All animals, both male and female, and all vegetables whatsoever, it is therefore evident are composed of living organic parts. These organic parts are in the greatest abundance in the seminal liquor of animals, and in seeds of vegetables. It is from the union of these organic parts returned from all parts of the animal or vegetable body, that reproduction is performed, and is always like the animal or vegetable in which it operates; because the union of these organic parts cannot be made but by the means of an internal mould, in which the form of an animal or vegetable is produced. It is in this also the essence of the unity and continuity of the species consists, and will so continue while the great Creator permits their existence.
But before I draw general conclusions from the system I am establishing, I must endeavour to remove some objections which might be made, and mention some other circumstances which will serve to place this matter in a better light.
It will be asked, why I deny those moving substances in the seminal liquors to be animals, since they have constantly been regarded as such by Leeuwenhoek, and every other naturalist, who has examined them? I may also be told, that living organic particles are not perfectly intelligible, if they are to be looked upon as animalculæ; and to suppose an animal is composed of a number of small animals, is nearly the same as saying that an organized being is composed of living organic particles. I shall therefore endeavour to answer these objections in a satisfactory manner.
It is certain that almost all naturalists agree in looking on the moving substances in seminal liquors as real animals; but it is no less certain, from my own observations, and those of Mr. Needham, on the seed of the calmar, that these moving substances are more simple and less organized beings than animals.
The word animal, in the acceptation we commonly receive it, represents a general idea formed of particular ideas drawn from particular animals. All general ideas include many different ones, which approach, or are more or less distant from each other, and consequently no general idea can either be exact or precise. The general idea which we form of an animal may be taken principally from the particular idea of a dog, a horse, and other beasts, which appear to us to act and move according to the impulse of their will, and which are besides composed of flesh and blood, seek after their food, have sexes, and the faculty of reproduction. The general idea, therefore, expressed by the word animal, must comprehend a number of particular ideas, not one of which constitutes the essence of the general idea, for there are animals which appear to have no reason, will, progressive motion, flesh nor blood, and which only appear to be a congealed substance: there are some which cannot seek their food, but only receive it from the element they live in: there are some which have no sensation, not even that of feeling, at least in any sensible degree: there are some have no sexes, or are both in one; there only belongs, therefore, to the animal a general idea of what is common also to the vegetable, that is, the faculty of reproduction.
The general idea then is formed from the whole taken together, which whole being composed of different parts, there is consequently between these parts degrees and links. An insect, in this sense, is something less of an animal than a dog; an oyster still less than an insect; a sea-nettle, or a fresh-water polypus, still less than an oyster; and as nature acts by insensible links, we may find beings which are still less animated than a sea-nettle, or a polypus. Our general ideas are only artificial methods to collect a quantity of objects in the same point of view; and they have, like the artificial methods we shall speak of, the defect of never being able to comprehend the whole. They are likewise opposite to the walk of nature, which is uniform, insensible, and always particular, insomuch that by our endeavouring to comprehend too great a number of particular ideas in one single word, we have no longer a clear idea of what that word conveys; because, the word being received, we imagine that it is a line drawn between the productions of nature; that all above this line is animal, and all below it vegetable; another word, as general as the first, and which is used as a line of separation between organized bodies and inanimate matter. But as we have already said, these lines of separation do not exist in nature; there are beings which are neither animals, vegetables, nor minerals, and which we in vain might attempt to arrange with either. For example, when Mr. Trembly first observed the polypus, he employed a considerable time before he could determine whether it was an animal or a plant; and possibly from this reason that it is perhaps neither one nor the other, and all that can be said is, that it approaches nearest to an animal; and as we suppose every living thing must be either an animal or a plant, we do not credit the existence of an organized being, that cannot be referred to one of those general names; whereas there must, and in fact are, a great number of organized beings which are neither the one nor the other. The moving substances perceived in seminal liquors, in infusions of the flesh of animals, in seed, and other parts of plants, are all of this kind. We cannot call these animals, nor can we say they are vegetables, and certainly we can still less assert they are minerals.
We can therefore affirm, without fear of advancing too much, that the grand division of nature's productions into Animals, Vegetables, and Minerals, do not contain every material being; since there are some that exist which cannot be classed in this division. We have already observed, that nature passes by insensible links from the animal to the vegetable, but from the vegetable to the mineral the passage is quick, and the distance considerable; from whence the law of nature's passing by imperceptible degrees appears untrue. This made me suppose that by examining nature closely we shall discover intermediate organized beings, which without having the power of reproduction, like animals and vegetables, would nevertheless have a kind of life and motion; other beings which, without being either vegetables or animals, might possibly enter into the composition of both, and likewise other beings which would be only the assemblage of the organic molecules I have spoken of in the preceding chapters.