GENERATION OF ANIMALS, III. viii.-ix. 



figure showing the way in which it is situated during 

 the process of formation, the Researches " should be 

 consulted. 



We have now spoken about the generation of the 

 animals that walk, fly and s\vim. Following the IX 

 plan we have laid down, there remain the Insects 

 and the Testacea to be discussed. We wiM deal wWh 

 the Insects first. 



I said earlier that some Insects are formed by (ii.) Repro- 

 means of copulation, others spontaneously ; further, insects :° 

 that they produce a larva, and I stated the cause of 

 their so doing. In a way, it looks as though practi- 

 cally all animals produce a larva to begin with, for 

 the fetation in its most imperfect state is something 

 of this sort ; and in all the Mvipara and all the 

 0\ipara that produce a perfect €:gg, the fetation in 

 its earhest stage is still undifferentiated and is grow- 

 ing, and this is just the sort of thing a larva is. At 

 the next step, some of the 0\ipara produce their 

 fetation as a perfect ^^g,, some as an imperfect one 

 which reaches its perfection after it has left the 

 parent, as I have often stated ^\■ith regard to fish. 

 In the case of the internally %'i\iparous animals, the 

 fetation, after it has been constituted at the outset, 

 in a way beconjes egghke : its fluid content becomes 

 enclosed in a fine membrane — like an egg with its 

 shell taken off — and that is why a fetation aborted 

 at this stage is known as an " efflux." * 



Those Insects which generate, generate larvae ; (a) Larrap. 

 and those Insects also which are formed spontane- 

 ously and not by means of copulation are, to begin 

 with, formed from an organism of this sort. This is 



» See H.A. 550 a 10 ff. 

 * Cf. H.A. 583 b 12. 



327 



