CHAPTER II 

 CONDITIONS OF CELLULAR IMMORTALITY 



In the preceding chapter it was pointed out that the 

 germ cells of higher organisms are potentially, and under 

 certain conditions in fact, immortal. What are the con- 

 ditions of immortality in this case? Are they such as 

 to support the thesis that the processes of mortality are 

 essentially physico-chemical in nature, and follow 

 physico-chemical laws? 



ABTIFICIAL PABTHENOGBNESIS 



The most essential condition of this immortality of 

 germ cells was mentioned, but not particularly empha- 

 sized. It is that two germ cells, an ovum and a spermato- 

 zoon unite, the process of union being called fertilization. 

 Having united, if they then find themselves in appro- 

 priate environmental conditions, development goes on; 

 new germ cells and a soma are formed, and the same 

 process keeps up generation after generation. Now, while 

 union of the germ cells is generally and in most organisms 

 an essential condition of this process, it is also true that 

 in a few forms of animal life, mostly found among the 

 invertebrates, development of the ovum can take place 

 without any preceding fertilization by a spermatozoon. 

 The process of reproduction, in this case is called par- 

 thenogenesis. In a number of forms in which partheno- 

 genesis never occurs normally, so far as is known, it can 

 be induced by appropriate extraneous procedures. The 

 discovery of this extraordinarily interesting and impor- 

 tant fact for a number of organisms, and the careful 



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