Preformation Theory

Jan SWAMMERDAM. From Biblia naturae, first published (tr. by H. D. Gaubius) as Bijbel de natuure, of, historie der insecten, tot zeekere zoorten gebracht: etc., Leyden, 1737 (posth.); tr. by T. Flloyd (revision by J. Hill as The book of nature or, the history of insects reduced to distinct classes, confirmed by particular instances, etc., London, 1758.

After an attentive examination of the nature and fabrick of the least and largest animals, I cannot but allow the less an equal, or perhaps superior degree in dignity. Whoever duly considers the conduct and instinct Of the one, with the manners and actions of the other, must acknowledge all are under the direction and controul of a supreme and singular intelligence; which, as in the largest, it extends beyond the limits of our comprehension, escapes our researches in the smallest. If, while we dissect with care the larger animals, we are filled with wonder at the elegant disposition of their limbs, the inimitable order of their muscles, and the regular direction of their veins, arteries, and nerves; to what an height is our astonishment raised, when we discover all these parts arranged in the least, in the same regular manner. How is it possible but we must stand amazed when we reflect that those animalcules, whose little bodies are smaller than the finest point of our dissecting knife, have muscles, veins, arteries, and every other part common to the larger animals? Creatures so very diminutive, that our hands are not delicate enough to manage, or our eyes sufficiently acute to see, them; insomuch that we are almost excluded from anatomizing their parts, in order to come at the knowledge of their interior construction. Thus, what we know of the fabrick of those creatures reaches no farther than to a simple enumeration of the parts which we have before observed in larger creatures. We are not only thus in the dark, in attempting a discovery of the construction of the least animalcules, but we even gain very little knowledge of the wonderful texture of the viscera of the largest animals: for as the point of our dissecting knife is not minute enough to separate the tender parts of the small animals, it is not less unfit to be used in discovering the extremities of the nerves and veins in the larger.

As our knowledge of both species of animals is so far limited by our ignorance, and as we have not hitherto had such a sufficient number of experiments as are necessary to form a proper judgment of their elegant structure, and the admirable disposition of their parts, we may easily see how rash and precipitate their opinion is, who esteem the larger creatures only as perfect, and the less as scarce worthy to be classed with animals; but, as they say, produced by chance, or generated from putrefaction; rendering, by such reasoning, the constant order of nature subject to chance. But as it happens to the smallest of animals, for instance, to those produced from the egg of the Acarus which is so minute, as scarcely to be visible, so also it is with the largest animals; their origin is not more obvious or more visible, perhaps it is rather more obscure, and they derive their being from a less visible beginning. Nor let any man imagine that I say this without conviction, since I have found by diligent inquiry that the largest animal is not in its first formation bigger than the rudiment of an Ant; and therefore, unless the Great Creator had set certain bounds to the growth of every kind, which it cannot exceed, I see no reason why the Ant might not surpass in bulk the largest. Perhaps, their sizes proceed in proportion to the greater or less strength of the heart, by which the parts must be extended, against the pressure of the atmosphere. Notwithstanding the smallness of Ants, nothing hinders our preferring them to the largest animals, if we consider either their unwearied diligence, their wonderful strength, or their inimitable propensity to labour; or, to say all in one word, their amazing and incomprehensible love to their young, whom they not only carry daily to such places as may afford them food, but, if by accident they are killed, and even cut into pieces, they, with the utmost tenderness, will carry them away piecemeal in their arms. Who can shew such an example among the largest animals, which are dignified with the title of perfect? Who can find an instance in any other creature, that may come in competition with this? But in the entrance of this work it is not my intention to explain the form and wonderful propagation of animalcules, which seem to be exsanguious or to have no blood: I shall treat in general of the manner of their surprising metamorphoses; and at the same time shew, that they not only resemble other animals in the increase of their parts, but that they exceed them by infinite degrees. ...

Though, amongst all the mutations of nature which deserve our attention, none appears more surprizing to the generality of mankind, than that by which a Caterpillar assumes the form of a winged animal, it in reality deserves no more admiration, than any other change in the forms of Bees, or the transformation observable in plants. This will evidently appear to any one, who, having examined the real nature of such metamorphoses, will observe how exactly they agree, not only with the growth of animals which undergo no such change; but also with the shooting or budding out of plants and flowers. Whatever difficulty we find in this, is merely an effect of our own mistaken notions; and our admiration arises from our ignorance of the nature of the Nymph or Chrysalis. In this the little animal lies, like the flower in its bud. Before I proceed farther on this head, it may be proper to observe, that these words, Nymph and Chrysalis, signify the same thing, and that there is no difference in the nature of the subjects to which they are applied. ...

That we may succeed the better in examining the nature of this Nymph, or Chrysalis, upon which, as upon an immoveable basis, the doctrine of all the changes observable in insects is so evidently founded, that the jarring opinions of all the naturalists who have hitherto wrote upon the subject, must appear utterly vain; it is necessary to observe, that the Nymph, or Chrysalis, is nothing more than a change of the Caterpillar or worm; or, to speak more properly, an accretion, growth, or budding of the limbs and parts of the Caterpillar or worm, containing the embryo of the winged animal that is to proceed from it. The Nymph, or Chrysalis, may even be considered as the winged animal itself hid under this particular form. From whence it follows, that in reality the Caterpillar, or worm, is not changed into a Nymph or Chrysalis; nor, to go a step further, the Nymph or Chrysalis into a winged animal; but that the same worm or Caterpillar, which, on casting its skin, assumes the form of a Nymph or Chrysalis, becomes afterwards a winged animal. Nor, indeed, can it be said that there happens any other change on this occasion, than what is observed in chickens, from eggs which are not transformed into cock or hens, but grow to be such by the expansion of parts already formed. In the same manner the Tad-pole is not changed into a Frog, but becomes a Frog, by an unfolding and increasing of some of its parts.

Hence it follows, that in the Aurelia, and more particularly in the Nymph, so called by Aristotle with the greatest propriety, there are not only all the parts and limbs of the little winged animal itself; but, what is more surprising, though ’till now unnoticed by any author I have met with, all these parts, or limbs, are to be discovered, and may be shewn in the worm itself, on stripping off its skin in a careful manner. If therefore we retain the name of Nymph, used by Aristotle, the worm at this period may be considered as marriageable, and, if we may make use of these expressions, entering into the connubial state. We may further shew this, by considering that the worms, after the manner of the brides in Holland, shut themselves up for a time, as it were to prepare, and render themselves more amiable, when they are to meet the other sex in the field of Hymen. ...

There are four orders which comprehend the whole class of insects, so that we cannot see one, which may not be referred to one or other of them, especially if we can see its change.

The first order will comprehend those insects, which, with all their limbs and parts, proceed instantly out of the egg, and grow insensibly, until they attain a proper size; after which they are changed into the Nymph, which undergoes no other change but that of its skin.

Of the second order are those hatched with six legs, and which, when the wings are gradually perfected, are also changed into Nymphs.

The third order is, when the Worm or Caterpillar comes forth from the egg either without any legs, or with six or more, and its limbs afterwards grow under the skin, in a manner imperceptible to our sight, until at length it casts that skin and resembles the Nymph, or Chrysalis.

The fourth order is, when the Worm likewise proceeds from the egg, either without any, or with six, or more legs, and in an invisible manner grows in its limbs and parts under the skin, and does not shed this skin, but acquires the form of a Nymph under it.