GENERATION OF ANIMALS, II. i. 



a general view, we may say that blooded animals are 

 larger than bloodless, and mobile ones larger than 

 stationary ; and they are the ones which emit semen 

 on account of their heat and their size.] 



We have now stated the Cause why each of the 

 two, male and female, is. 



Some animals bring their young to perfection, and The various 

 bring forth externally a creature similar to them- generation. 

 selves — e.g., those which are externally \iviparous ; 

 others produce something which is unarticulated and 

 has not yet assumed its proper shape. In the latter 

 class those which are blooded lay eggs, those which 

 are bloodless produce (either eggs or) larvae.** The 

 difference between an eg^ and a larva is this : an 

 cg^g is something from part of which the new creature 

 is formed, while the remainder is nourishment for it ; 

 whereas in the case of the larva, the jvhole of it is used 

 to form the whole of the offspring.'' Of the animals 

 which produce externally a perfected creature similar 

 to themselves, i.e., the \ ivipara, some are internally 

 viviparous from the outset (as man, horse, ox ; and 

 of sea-creatures, the dolphin and the other animals 

 of that sort), others are internally oviparous at the 

 first stage, and thereafter are externally viviparous 

 (as what are called Selachia). Of oviparous animals, 

 some lay their eggs in a perfected state (as birds, 

 oviparous quadrupeds and footless animals, e.g., 

 Hzards and tortoises, and the great majority of the 

 serpents '")— eggs which on6e they are laid do not 

 grow any more ; others lay their eggs in an imper- 



ment, and the utilization of tissue-disintegration products in 

 metamorphosis. The embryo feeds upon its yolk, but the 

 pupa feeds upon itself. 



' The viper is the exception ; see below, line 21. 



135 



