41 THE HISTORY OF BIOLOGY 



always, man — represents the more complete, "warmer" element, and the 

 female, the woman, the more incomplete, the "colder" element. The mascu- 

 line represents, above all, form, motion, activity; the feminine is matter, 

 the passive, and consequently potentiality, which achieves reality through 

 form. It is expressly asserted that the earth represents in the universe the 

 womanly and maternal, the sun the manly — • that is to say, the ancient 

 view held by most natural religions. The male sex-product, the seed, is a 

 product of the blood, which through complete "cooking" receives the 

 purest and most form-creating qualities. The woman's sex-product is the 

 menstrual blood, which is an undeveloped sperm — "half cooked," because 

 the woman is weaker, "colder" than man, and has not the power to cook her 

 product completely. In impregnation the man contributes to the future child 

 form, motion, soul; the woman matter, body; his contribution is compared 

 with the work of a carpenter, hers with the timber of which things are made. 

 Holding this view of reproduction, Aristotle, when making his thorough in- 

 vestigation into the question of heredity, can of course only involve himself 

 still deeper in abstract speculations. Against the opinion of earlier philoso- 

 phers that the seed is derived from all parts of the body and therefore gives 

 rise to similar individuals as issue, he asserts that on the contrary the seed 

 goes to the different parts of the body, through which process a remainder 

 is left over for the next generation, "as with a portrait-painter, a certain 

 amount of colour is left over similar to that which was used for the portrait. ' ' 

 If the man's form-building power is sufficiently strong, the child will be a 

 boy; otherwise a girl; for that reason very young and very old fathers have 

 mostly girl-children. The cold north wind also favours the birth of girls, for 

 warmth is strength. The explanation of why children resemble partly their 

 parents and partly their ancestors is very complicated and ingenious, for all 

 its abstractness, but it would take too long to examine it here. Of far greater 

 value than these metaphysical speculations, at any rate, are Aristotle's 

 observations on the reproduction of animals. He draws up a scale in which 

 the animals are placed according to their development and points out that 

 those animals are highest which have a warm and moist, and not an earthy, 

 nature. For all animals with lungs are warmer than those without lungs, 

 and of those provided with lungs, again, the warmest are those which have 

 not tough, spongy, and anasmic, but soft and sanguineous lungs. The most 

 perfect animals, those which possess most warmth and moisture, whose 

 young are born alive and immediately start growing, are the mammals; 

 those which possess moisture, but less warmth lay eggs which afterwards 

 develop inside the female animal and are born alive: sharks. Warm and dry 

 animals lay "complete" eggs, such as birds and reptiles; cold and earthy ani- 

 mals lay "incomplete" eggs, such as osseans, frogs, and ink-fish; and finally 

 the lowest animals of all — that is, of those that propagate in a sexual 



