GENERATION OF ANIMALS, III. i. 



[(no bloodless animal lays eggs)], the blood, as I 

 have often stated, being the matter for animal organ- 

 isms. One part of the egg, the hot part," is closer 

 to the form of the developing creatures ; the other, 

 the more earthy part, supplies the wherewithal for 

 building up the bodily frame and is further removed 

 from the form.** That is why in the case of all double- 

 coloured eggs the young animal gets its " principle 

 of generation from the white, because hot substance 

 is the place where the soul-principle is to be found, 

 while it gets its nourishment from the yolk.'' With 

 those animals, therefore, whose nature tends to be 

 hotter than others we find there is a clear distinction 

 between the part from which the " principle " is 

 formed and the part from which the nourishment is 

 derived : the one is white, the other yellow, and there 

 is always more of the pure, white part than there is 

 of the earthy, yellow part. With the animals that 

 are less hot and more fluid, there is more yolk in the 

 egg and it is more fluid. This occurs in the case of 

 the marsh-birds, since they are more fluid and colder 

 in their nature than the land-birds, so that the eggs 

 of such birds contain a great deal of what is called 

 yelk (lekithos) and it is less yellow, because the white 

 is less distinctly separated from it. Pass on a further 

 stage to those oviparous animals which are cold in 

 their nature and also still more fluid (the fish tribe 

 answers to this description), and in their eggs the 

 white is not distinct at all ; this is due to their small 

 size and to the abundance of the cold and earthy 

 matter. And that is why all fishes' eggs are single- 

 yolk ; and it was again Harvey who demonstrated that 

 the " cicatricula " was the point of origin of the embryo, 

 " the first Principle of the Egge." 



279 



