GENERATION OF ANIMALS, III. ii. 



what means do eggs get theirs ? (The possibiUty 

 that they are themselves their own means of growth, 

 as larvae are," may be ruled out.) If there is some- 

 thing by means of which the egg is fastened on, what 

 happens to it when the egg has reached its perfec- 

 tion ? It does not come out along with the egg, as 

 the umbilical cord does in the case of animals,* 

 because when the egg has reached perfection, the 

 shell is formed which envelops it. Well, this is a 

 question which it is quite right to ask ; but those who 

 ask it fail to notice that the shell as it forms is at first 

 a soft membrane, and that it is only when the egg 

 has been perfected that it becomes hard and brittle ; 

 and this adjustment is so well timed that it is still soft 

 when it leaves the bird (othervWse it would be painful 

 to lay), but as soon as it has left the bird it cools, and 

 that makes it set hard, for the fluid part quickly 

 evaporates, being verj- small in quantity, while the 

 earthy part remains behind. Now at the outset a 

 portion of this membrane, at the pointed end of an 

 egg, is like an umbihcal cord, and while the egg is 

 still small, it sticks out Uke a pipe. It can be clearly 

 seen in small, aborted eggs : if the hen is drenched 

 (with cold water) or chilled in some other way and 

 so drops (the fetation) before its time, the fetation 

 still has a blood-like appearance and has a small 

 tail,*^ Uke an umbiUcal cord, running through it ; as 

 the fetation gets larger, this tail gets twisted round 

 more and becomes smaller ; when (the fetation) 

 has reached its complete development, this terminus 

 finishes up as the pointed end of the egg. Under- 

 neath this is the inner membrane, which acts as a 

 boundary between it on the one side and the white 

 and the yolk on the other. When the development 



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