Generation of Animals & History of Animals I, Parts of Animals I by Aristotle

Author:Aristotle [Aristotle]
Language: eng
Format: epub
ISBN: 9781624668272
Publisher: Hackett
Published: 2019-10-03T00:00:00+00:00

IV 4

Now Democritus |769b30| said that monsters come to be because two semens fall [into the uterus], one setting [the menses] in movement earlier, the other later, and this latter, once it issues forth, arrives in the uterus, so that the parts [of the embryo] grow together and become confused.777 But in the birds, he says, since mating always takes place quickly, both the eggs and their color |769b35| become confused.778 But if several offspring come to be from one semen and one act of sexual intercourse, which is just what appears to be the case, |770a1| it is better not to go the long way around, passing the short one by.779 For especially in such cases it is necessary for this to occur when the seeds are not disaggregated but instead arrive together [in the uterus]. If, then, we must attribute the cause to the semen from the male, that |770a5| is the way we would have to state it. But, in general, we must rather think that the cause resides in the matter [contributed by the female] and in the embryos being composed.

That is why too monsters of these sorts come to be altogether rarely in uniparous animals, but more frequently in the multiparous ones, and most of all in birds, and among birds most of all in chickens. For this bird |770a10| is multiparous not only in laying often, like the pigeon genus, but also because it has many embryos at the same time and mates all year round. That is also why it lays many twin-eggs. For the embryos grow together because they are close to each other, as many fruits sometimes do. |770a15| Of these twin-eggs, when the yolks are divided by the membrane, two separate chicks come to be having nothing extraordinary about them, but when the yolks are continuous, with nothing keeping them asunder, from these, chicks that are monstrous come to be, having one body and head but four legs and four wings. This is because the |770a20| upper parts come to be earlier from the white, the nourishment for them being dispensed from the yolk, whereas the lower part develops later and its nourishment is one and indivisible.780

Also already observed is a serpent that is two-headed due to the same cause. For this genus too is multiparous and lays many eggs. Monstrosities, however, are more rare |770a25| in their case due to the shape of the uterus. For because of its length the large number of eggs are set in a row.781 And where bees and wasps are concerned nothing of this sort occurs, because their offspring are in separate cells. But where {147} chickens are concerned the contrary is the case, which makes it clear that |770a30| we must consider the cause of these things to reside in the matter. For among the other animals too monstrosities occur more often in those that are multiparous. That is why in the human they are less common. For it is for the

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