ON GENERATION. 335 



proper size, which never attains to any larger growth after it is 

 first born ; this is called metamorphosis. But the more perfect 

 animals with red blood are made by epigenesis, or the su- 

 peraddition of parts. In the former, chance or hazard seems 

 the principal promoter of generation, and there, the form is 

 due to the potency of a preexisting material; and the first 

 cause of generation is ' matter,' rather than ' an external 

 efficient ;' whence it happens too that these animals are less 

 perfect, less preservative of their own races, and less abiding, 

 than the red-blooded terrestrial or aquatic animals, which owe 

 their immortality to one constant source, viz. the perpetuation 

 of the same species ; of this circumstance we assign the first 

 cause to nature and the vegetative faculty. 



Some animals then are born of their own accord, concocted 

 out of matter spontaneously, or by chance, as Aristotle seems 

 to assert, when he speaks of animals whose matter is capable of 

 receiving an impulse from itself, viz. the same impulse given 

 by hazard, as is attributable to the seed, in the generation of 

 other animals. A^id the same thing happens in art, as in the 

 generation of animals. Some things, which are the result of 

 art, are so likewise of chance, as good health ; others always 

 owe their existence to art; for instance, a house. Bees, wasps, 

 butterflies, and whatever is generated from caterpillars by 

 metamorphosis, are said to have sprung from chance, and 

 therefore to be not preservative of their own race ; the con- 

 trary is the case with the lion and the cock ; they owe their 

 existence as it were to nature or an operative faculty of a 

 divine quality, and require for their propagation an identity of 

 species, rather than any supply of fitting material. 



In the generation by metamorphosis forms are created as if 

 by the impression of a seal, or, as if they were adjusted in a 

 mould ; in truth the whole material is transformed. But an 

 animal which is created by epigenesis attracts, prepares, ela- 

 borates, and makes use of the material, all at the same time ; 

 the processes of formation and growth are simultaneous. In 

 the former the plastic force cuts up, and distributes, and re- 

 duces into limbs the same homogeneous material ; and makes 

 out of a homogeneous material organs which are dissimilar. 

 But in the latter, while it creates in succession parts which are 

 differently and variously distributed, it requires and makes a 



