763 b 20 I HepL fiev ovv rrjs yeveaews rrjg ra>v t,(l)U)v etprjTaL 

 Kai Koivfj Kal ;^a)pts" Trepl ttolvtcov. errel S' ev rot? 

 TeAecoTctTots" aLvru)v earl to dijXv /cat to dppev 

 Kextjopiajjievov, Kal Tay'ra? tols Sfva/xei? dpxo-S 

 (f)ap.ev elvai ttolvtcov Kal l^cpcov Kal <^vt(2)v, aXXd to. 



25 fJL€v ainds dxcuptcrrovs ex^t to. §€ Kex^jptapievas , 

 AeKT€ov 7T€pl TTJs yeveacojs ttjs tovtojv rrpojTov 

 €Ti yap OLTcXcov ovTCov €v TO) yev€L Siopi^eTat to 

 drjXv Kal TO dppev. TTOTepov Se Kal Trplv hrjXrjv 

 Trjv SLa(f)opdv etvai Trpos Trjv atadrjaiv rjiiaJv to fxev 

 drjXv TO 8' dppev ioTiv, iv Tjj pbrjTpl Xa^ovTa ttjv 



30 hiatjiopdv rj TrpoTcpov, dp.(f)ta^r)TeLTai . (ftaal ydp 

 OL fxev iv Tols GTTepixaaLv elvai TavTr]v ttjv evav- 

 tLcoolv evdvs, otov 'Ava^ayopas Kal eVepot tcov 

 (jtvaioXoyajv yiveadai t€ ydp c/c tov dppevos to 



" See Introd, § 76. 



'' See Introd. § 26. " See Introd. § 11. 



"* The first microscopically visible signs of sex-diiferentia- 

 tion occur about the fifth day in the chick. Aristotle was 

 quite justified in his belief that sex-differentiation occurs 

 early. We know to-day that sex is determined genetically 

 from the moment of fertilization, since some animals have 

 two kinds of sperm and others have two kinds of egg. 

 370 



