ON GENERATION. 303 



EXERCISE THE THIRTY-SIXTH. 



The perfect hen's egg is of two colours. 



Every egg, then, is not perfect ; but some are to be held im- 

 perfect because they have not yet attained their true dimen- 

 sions, which they only receive when extruded ; others are im- 

 perfect because they are yet unprolific, and only acquire a 

 fertilizing faculty from without, such are the eggs of fishes. 

 Other eggs again are held imperfect by Aristotle, because they 

 are of one colour only, inasmuch as perfect eggs consist of yelk 

 and albumen, and are of two colours, as if better concocted, 

 more distinct in their parts, endowed with higher heat. The 

 eggs that are called centenine or hundredth eggs, and which 

 Fabricius 1 will have it are engendered of certain remainders of 

 albumen, are of one colour only, and by reason of their de- 

 ficiency of heat and their weakness, are regarded as imperfect. 

 Of all eggs, there are none more perfect than those of the hen, 

 which are produced complete in all their fluids and appendages, 

 of proper size and fruitful. 



Aristotle assigns the following reason wherefore some eggs 

 are of two colours, others of one hue only : 2 "In the hotter 

 animals those things from which the principles of their origin 

 are derived, are distinct and separate from those which furnish 

 their nutrition; now the one of these is white, the other is 

 yellow/' As if the chick derived its origin from the albumen 

 and was nourished by the vitellus alone. In the same place 

 he proceeds thus : " That part which is hot contributes properly 

 to the form in the constitution of the extremities ; but the part 

 that is more earthy, and is further removed, supplies material 

 for the trunk. Whence in eggs of two colours the animal 

 derives its origin from the white, for the commencement of 

 animal existence is in the white ; but the nourishment is ob- 

 tained from the yellow." He consequently thinks that this is 

 the reason why these fluids are distinct, and why eggs are 

 produced of two colours. 



1 Op cit. p. 10. 2 De Generat. Animal, lib. iii, cap. 1. 



