30 



GENERAL PRELIMINARY CONSIDERATIONS. 



accordance with a determined type, and every individual of a 

 species repeats the organisation of its parents without any 

 considerable or abnormal deviation from it. And it is well 

 known that this is the case not only with reference to the mere 

 existence or I'eproduction of the same organs, but with regard, 



above all, to their position. This topography of the organs of 

 an animal is, to say the least, of quite equal significance with 

 the existence of the individual organs ; so much so that the 

 development of our modern views as to the embryology of 

 animals the history of their individual growth rests essen- 



