What I have said will appear more clear, if we consider the formation and growth of the eggs of fish; when the female deposits them in the water they are only the outlines of eggs, which being separated from the body of the animal, attract and appropriate to themselves the particles which agree the best for their nourishment, and grow thus by intussusception. In the same manner as the hen's egg acquires the white and membranes in the matrix, wherein it floats, so the eggs of fish acquire their membranes and white in the water; and whether the male impregnates them, by emitting on these the liquor of its roe, or whether they remain unimpregnated, they do not the less attain their entire perfection. It appears to me, therefore, that the eggs should be considered as organized bodies, which being neither animals nor vegetables, are a genus apart.
A second class of beings, of the same kind, are the organized bodies found in the semen of all animals, and which, like those in the milt of a calmar, are rather natural machines than animals. These are properly the first assemblages which result from the organic molecules we have so much spoken of, and they are, perhaps, the parts which constitute the organized bodies of animals. They are found in the semen of all animals, because the semen is only the residue of the organic molecules that the animal takes in with its aliment, and which, as we have already observed, are those parts most analogous to the animal itself, and most organic; it is those particles which compose the matter of the semen, and consequently we must not be astonished to find organized bodies therein.
To be perfectly convinced that these organized bodies are not real animals, we need only reflect on the preceding experiments. The moving bodies in the seminal liquor have been taken for animals, because they have a progressive motion, and are thought to have a tail; but if we consider, on one hand, the nature of this progressive motion, which finishes in a very short time without ever renewing its motion; and on the other, the nature of these tails, which are only threads which the moving bodies draw after them, we shall begin to hesitate; for an animal goes sometimes slow, sometimes fast, and sometimes remains in a state of rest; these moving bodies, on the contrary, always continue the same motion, and I have never seen them stop and renew their movement again. I ask, whether this kind of continued motion, without any rest, is common to animals, and if that ought not to make us doubt these moving bodies being real animals? An animal of any kind must also have a constant form and distinct limbs; but these moving bodies vary, and change their forms every moment, have no distinct limbs, and their tails appear as a part which does not belong to the individual. Can we then imagine these bodies to be real animals? In seminal liquors filaments are seen which lengthen and appear to vegetate; after which they swell and produce moving bodies. These filaments may be kinds of vegetables, but the moving bodies which spring from them cannot be animals, for a vegetable has never yet been seen to produce an animal. These moving bodies are found in all vegetable and animal substances; they are not produced by the modes of generation, they have no uniformity of species, and therefore can neither be animals nor vegetables. They are to be met with in the flesh of animals, and in the substance of vegetables, but are most numerous in their seeds; is it not therefore natural to regard them as living organic particles which compose the animal or vegetable; as particles which having motion and a kind of life, ought, by their union, to produce moving and living beings, and so form animals and vegetables?