14 INDIVIDUALITY IN ORGANISMS 



union results in a new individuation. In the higher 

 animals this form of reproduction is, with very rare 

 exceptions, the only process which gives rise to organisms. 



Apparently gametic and agamic reproduction are 

 very different processes, but we must at least raise the 

 question whether they are similar in any way, or, if 

 they are different, what the difference may signify. 



It is in those parts of pre-existing individuals which 

 become new whole individuals that the process of indi- 

 viduation goes on before our very eyes, and it is there 

 that we have the opportunity to determine something of 

 its nature. It is by no means necessary for us to wait for 

 the occurrence of reproduction in nature. In many 

 of the simpler organisms we can bring about the occur- 

 rence of reproduction at will, simply by cutting out 

 pieces of the body and so isolating them from their 

 physiological relations with other parts. Such pieces 

 may become new organisms or parts of organisms more 

 or less like those from which they were taken. These 

 experimental reproductions constitute, as I shall show, 

 invaluable material for the study of the organic indi- 

 vidual and of the process of individuation, although their 

 value for this purpose has not heretofore been generally 

 recognized. 



METABOLISM AND PROTOPLASM 



The living organism consists of a substance, or more 

 properly a complex mixture of substances, in which the 

 series of chemical reactions known as metabolism 

 occurs. The fundamental constituents of protoplasm 

 occur in what is known as the colloid condition, i.e., they 

 do not form a true molecular solution, but exist as sus- 



