GENERATION OF. ANIMALS, III. iv. 



grows by its own means and not in virtue of any 

 attachment.'' The reason for this is on a par \\ith 

 the reason why yeast grows. Yeast, hke these, is 

 small in bulk to start A\ith anH gets larger : this 

 growth is due to its more sohd portion turning fluid, 

 and the fluid turning into pneuma.^ This is the 

 handiwork of the soul-heat '^ in the case of animals, of 

 the heat of the humour blent with it in the case of the 

 yeast. Eggs thus grow of necessity on account of this 

 cause (/.e., they contain a yeast-like residue''), but 

 also they grow /or the sake of rvhat is better, since it is 

 impossible for them to obtain all their gro^\■th in 

 the uterus owing to the prolific habit of these animals. 

 That is why the eggs are quite small when they are 

 discharged and why they grow quickly : they are 

 small because the uterus is not roomy enoug-h to hold 

 so large a number of eggs, and they grow quickly to 

 prevent the destruction of their kind which would 

 occur as a result of their spending a long time over 

 the growing period of their formation. Even as it is, 

 the majority of the fetations that are laid externally 

 get destroyed. That is why the fish tribe is proHfic : 

 Nature makes good the destruction by sheer weight 

 of numbers. There are also some fishes, such as the 

 one known as belone,^ which burst asunder owing to 

 the size of the eggs, the fetations of this fish being 

 large instead of numerous ; here Nature has taken 

 away from their number and added to their size. 



I have now described the growth of eggs of this 

 sort and h«tve stated the Cause of it. 



Synffnuthus acus. In tliis group (of which the well-known 

 " sea-horoc " is another member) the male incubates the eggs 

 in a brood-pouch formed by the pelvic fins. Aristotle cor- 

 rectly states at H.A. loc. c'lt. that the fisb is none the worse 

 for its " bursting asunder." 



305 



