ARISTOTLE 



Claasiflca- 

 tion 

 according to 

 method of 

 reproduc- 

 tion. 



' ' Perfect 

 animals. 



Distinction 

 of ' ' per- 

 fect" and 

 "imperfect" 

 «gg«. 



Distinction 



of egg 



and larva. 



the very end and then says that strictly speaking they 

 ought not to move about at all, yet in fact we see them 

 moving : anyway, their movement is " contrary to 

 nature," because they " have no right and left ." (The 

 mechanism of their movement can be detected only by 

 the microscope, and is known as ciliary.) 



(76) In G.A., however, although Aristotle adheres to his 

 classification into Blooded and Bloodless animals, per- 

 haps a more important classification is that which is 

 based upon their method of reproduction. This classi- 

 fication will be found in the Contents-Summary, 

 pp. Ixii ff. And in this connexion we must notice that 

 the list is headed by the Viviparous animals, of which 

 the first is Man : these are the " most perfect animals," 

 and therefore they produce their offspring in the most 

 perfected condition. And by " most perfect " (732 b 29) 

 Aristotle means the animals which are " in their nature 

 hotter and more fluid {vyporepa), and are not earthy " ; 

 and, as the test of natural heat is the presence of the 

 lung, and further, a lung well supplied with blood, no 

 animal can be internally viviparous unless it respires. 

 (See the whole passage 732 a 26—733 b 16.) 



(77) It should be noted that Aristotle clearly distinguishes 

 between what he calls " perfect " and " imperfect " 

 eggs, that is to say between eggs which do not and those 

 which do increase in size after deposition. This is the 

 basis of the modern distinction between cleidoic and 

 non-cleidoic eggs (see 718 b 7, n.). He also clearly 

 distinguishes between an egg and a larva : an egg is 

 that from part of which the young creature is formed, 

 the remainder serving as nourishment for it ; a larva 

 is something of which the ichole is used to form the 

 young animal. (See 732 a 29 and note, and 758 b 10 flF.) 

 The fact that Aristotle drew these distinctions so clearly 

 is particularly noteworthy. He was, of course, unaware 

 of the existence of the mammalian ovum, which cannot 

 be detected without the aid of the microscope. It 

 should also be noted that Aristotle compares the growth 

 of a non-cleidoic egg with the action of yeast in fermenta- 

 tion ; see 755 a 18. 



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