CHAPTER X 



THE FERTILISATION OF THE EGG 



In the foregoing summary we have taken the existence of an 

 animate unit or individual for granted, considering its character- 

 istic properties, their sources of energy and the way in which 

 they are brought into working relationship with one another 

 and with the external world. It is one of the characteristic 

 properties of animate systems that they are self-propagating. 

 The quantitative analysis of this property is therefore an 

 important branch of physiology. In spite of the immense 

 volume of careful quantitative work in this field, the important 

 fact that living organisms reproduce their kind — and that the 

 power to do so is one of the most remarkable features which 

 characterise living beings— is customarily neglected in physio- 

 logical text-books or summarily treated from a teleological 

 standpoint which betrays little sympathy with the advances 

 which have been made in the last two decades through the 

 work of Loeb on fertihsation and the rediscovery of Mendel's 

 method in the opening years of the twentieth century. The 

 explanation of this omission is to be sought chiefly in the fact 

 that, while exact knowledge of metaboUsm, muscle, nerve, 

 and respiration has been advanced chiefly by studies on the 

 higher animals, practically every important discovery in the 

 field we are now about to consider is based on material of 

 too humble origin to interest the medical man. Nevertheless 

 conclusions derived from these studies are, as will be seen, of 

 wide applicability. For this reason a very brief outline of 

 existing knowledge of the mechanics of reproduction will now 

 be given. The subject is full of interest on the bionomic side 

 in connection with the possibility that living organisms are 



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