198 GENEEATION AND DEVELOPMENT. « 



parts, such as, for example, the Hver, lungs, and eyes, were 

 produced from it, just as a man is produced from a child, 

 but not by the child. 



Further, he says that the young animal is not at once a 

 horse or a man, but that its life is at first like that of a 

 plant, and that the characteristics of each kind of animal are 

 the last to be developed.* This seems to foreshadow the 

 modern theory that the history of the development of the 

 individual is an epitome of the history of the evolution of 

 the species. 



A most difficult question in embryology is that dealing 

 with the causes determining the sex of the young animal. 

 This question was discussed before Aristotle's time, and has 

 been discussed until the present day. Anaxagoras believed 

 that the distinction depended on the position of the sperm 

 itself in the uterus, Empedocles that it depended on the 

 temperature of the uterus, a hotter uterus bringing forth a 

 male and a colder one a female, and Democritus believed that 

 the distinction depended on the preponderance, in some way, 

 of one or other of the sperms, male and female. Aristotle 

 was inclined to adopt a view similar to that of Democritus, 

 and seemed to regard the action between the sperms to be of 

 the nature of a contest, the sex of the young animal corre- 

 sponding with that of the sperm which overpowered the 

 other, t As late as the year 1898, a theory of this kind was 

 set forth by Dr. Leopold Schenk, of Vienna. I Generally 

 speaking, this theory was the opposite of Aristotle's, for 

 Schenk's view was that the tendency was for offspring to 

 take the sex opposite to that of the more vigorous parent. 



Aristotle's statements about spontaneous generation have 

 been discussed in Chapter v. It was easy for the Ancients 

 to persuade themselves that spontaneous generation com- 

 monly occurred, for they had no means of knowing that, in 

 matter believed by them to be lifeless, there existed countless 

 germs giving rise to numerous forms of life. Some even 

 believed that the spontaneous generation of mankind was 

 possible. Aristotle's views were less extravagant, but he 

 believed that eels, many of his Entoma,^ and most of his 

 Ostrakoderma,\\ were generated spontaneously. He says 

 that eels had never been found with milt or roe, that, when 

 opened, they did not seem to possess generative organs, and 



=■= G. A. ii. c. 3, 7366. f G. A. iv. c. 1. 



\ Schenk's Theory : The Determination of Sex, London, 1898. 



§ if. ^. V. c. 17, s. 2. II H. A. V. c. 13 ; G. A. iii. c. 11, 7016. 



