GENERATION OF ANIMALS, TV. iv. 



of a single animal, it is not possible that the entirety 

 of this should be used to form one embryo ; on the 

 contrary, as many are formed as is determined by 

 the sizes proper to those animals. Nor again will the 

 semen of the male or the dynamis " residing in the 

 semen put into shape anything that is greater or less 

 than the natural size. Similarly, if the male emits 

 more semen, or more dynameis in the semen (in cases 

 where the semen gets divided up), the greatest 

 possible amount will not make anything bigger (than 

 the natural size), but on the contrary will dri^ the 

 material up ** and destroy it. The parallel case of 

 fire and water shows this. An increase in the amount 

 of fire does not mean that the fire increases the heat 

 of the water in the same ratio ; on the contrary, there 

 is a limit to the heat, and when that has been reached, 

 you may increase the amount of fire, but the water 

 does not continue to get hotter ; instead it evapor- 

 ates more, and finally disappears and dfies up. Now 

 since, as it seems, there must be some proportional 

 relationship <^ between the residue of the female and 

 that which comes from the male (this applies where 

 the males emit semen), in the case of those animals 

 which produce many offspring the male at the outset 

 emits semen which is able, when divided up into 

 portions, tcgive shape to a number of fetations, while 

 the female contributes enough material so that a 

 number of fetations can take shape out of it. (The 

 parallel instance of milk, which was cited,** is not com- 

 parable, since, in the case of that which the semen's 

 heat causes to take shape, not only quantity is in- 

 volved but also quality, whereas in the case of the 

 heat in the fig-juice and the rennet, quantity alone is 

 involved.) * This, then, is the reason why in those 



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