ARISTOTLE AS A NATURALIST. 29 



conceives the evolution of the individual to be a new 

 formation, in which the several parts of the body develop 

 one after the other. According to him, when the human 

 or animal individual develops, either within the mother's 

 body or out of it in the egg, the heart is formed first, and 

 is the beginning and the centre of the body. After the 

 heart has been formed, the other organs appear ; of these 

 the interior precede the exterior, and the upper, or those 

 above the diaphragm, precede the lower, or those below it. 

 The brain is formed at a very early stage, and out of it 

 grow the eyes. This assertion is, indeed, quite accurate. On 

 trying to obtain from these statements of Aristotle an idea 

 of his conception of the processes of evolution, we find that 

 they indicate a faint presentiment of that theory of evolution 

 which is now called Epigenesis, and which Wolff, some two 

 thousand years later, first proved. It is especially remark- 

 able that Aristotle altogether denied the eternity of the 

 individual. He admitted that the kind or species, formed 

 from individuals of the same kind, might possibly be 

 eternal ; but asserted that the individual itself was tran- 

 sient, that it came into being anew in the act of genera- 

 tion, and perished at death. 



During the two thousand years after Aristotle no 

 essential progress in Zoology in general, or in the History of 

 Evolution in particular, is to be recorded. People were 

 content to expound Aristotle's zoological writings, to copy 

 them, to deface them greatly by additions, and to translate 

 them into other languages. There was hardly any 

 independent research during this long period. During the 

 Middle Ages of Christianity, when insurmountable obstacles 

 were laid in the way of independent researches in 



