Generation of AnimalsAristotle
About Generation of Animals
Aristotle's is his principal work on animal reproduction, embryology, and heredity. and the other biological treatises had treated formal, material, and final causes; this work takes up the efficient cause, that from which the movement of generation begins. It consists of five books.
Book I surveys the reproductive organs of blooded and bloodless animals and develops the theory of semen. Semen is not a waste product but a residue of useful nutriment. The male contributes the efficient and formal principle; the female contributes the material. Book II continues the account of semen as a compound of pneuma (breath or vital heat) and water, and explains how the male imparts soul as capacity for function rather than as a separate substance implanted from without. The embryo develops by successive formation of parts (epigenesis), not by the unfolding of a miniature already complete in the seed. The heart appears first. The female can produce wind-eggs and so can impart the nutritive soul alone; the higher faculties require the male. Book III treats eggs, birds, fish, insects, bees, and the spontaneous generation Aristotle attributes to some testacea. Book IV turns to sex determination, resemblance to parents and ancestors, and deformities: when the male principle fails to master the material, the offspring tends toward the female or toward more distant ancestral traits. Book V discusses variations in non-essential features such as eye color, hair, and the pitch of the voice.
The treatise is the classical source for the claim that generation is the transmission of form into matter, for the epigenetic account of development, and for a theory of inheritance that explains both likeness and departure from the parents. Harvey's later works against and with this framework; modern embryology abandoned the male-form and female-matter dualism while retaining the problem Aristotle first organized as a single science of how animals come to be.