Generation of Animals

The Generation of Animals (or On the Generation of Animals; Greek: Περὶ ζῴων γενέσεως (Peri Zoion Geneseos); Latin: De Generatione Animalium) is one of the biological works of the Corpus Aristotelicum, the collection of texts traditionally attributed to Aristotle (384–322 BC).

Book I (715a – 731b) Chapter 1 begins with Aristotle claiming to have already addressed the parts of animals, referencing the author's work of the same name.

While this and possibly his other biological works, have addressed three of the four causes pertaining to animals, the final, formal, and material, the efficient cause has yet to be spoken of.

The hedgehog's form is that of an animal able to use its spines for self-defence, and so its reproductive organs are situated in such a way as to complement this.

This is continued in chapters 12 and 13, where Aristotle discusses the reasons the uterus is internal and the testes external, and their locations among various species.

Concluding this section on the reproductive parts of animals is an overview from chapters 14–16 of the generative faculties of crustacea, cephalopods, and insects.

[2] The remainder of Book I (chapters 17 – 23) is concerned with providing an account of semen and its contribution to the generative process.

This is the basis for the imparting of the soul upon the material substratum present in the egg, as the female reproductive residue itself contains no active principle for the motion required to form an embryo.

In chapter 5 the theory of soul-imparting is amended slightly, as observations of wind-eggs show that the female, unassisted, is able to impart the nutritive aspect of the soul, which Aristotle claims is its lowest portion.

Chapters 5 and 6 are a response to what Aristotle takes to be falsely-held beliefs of other scientists concerning the process of procreation.

Chapters 7–10 cover the generative processes of selachians, cephalopods, crustacea, insects and bees, in successive order.

Aristotle is concerned with both the similarities between the offspring and parents and the differences that can arise within a particular species as a result of the generative process.

In chapter two Aristotle provides pieces of observational evidence for this, including the following:"Again, more males are born if copulation takes place when north than when south winds are blowing; for animals' bodies are more liquid when the wind is in the south, so that they produce more residue – and more residue is harder to concoct; hence the semen of the males is more liquid and so is the discharge of the menstrual fluids in women.

The apparent lack of a single causal scheme or subject matter for these discrete topics has led to disagreement in how this book relates to the rest of the Generation of Animals.