LECTURE XII 



CONCLUDING REMARKS 



BIOLOGISTS are confronted with two problems of transformation; 

 namely, the artificial transformation of dead into living matter, and the 

 artificial transformation of one species of plants or animals into another. 

 Will it be possible to solve these problems? It is certain that nobody 

 has thus far observed the transformation of dead into living matter, and 

 for this reason we cannot form a definite plan for the solution of this 

 problem of transformation. But we see that plants and animals dur- 

 ing their growth continually transform dead into living matter, and that 

 the chemical processes in living matter do not differ in principle from 

 those in dead matter. There is, therefore, no reason to predict that 

 abiogenesis is impossible, and I believe that it can only help science 

 if the younger investigators realize that experimental abiogenesis is the 

 goal of biology. On the other hand, our lectures show clearly that we 

 can only consider the problem of abiogenesis solved when the artificially 

 produced substance is capable of development, growth, and reproduc- 

 tion. It is not sufficient for this purpose to make proteins synthetically, 

 or to produce in gelatine or other colloidal material round granules 

 which have an external resemblance to living cells. 



In this connection another problem may be mentioned; namely, 

 whether there exists a natural death or, in other words, whether death 

 is the necessary outcome of development, and whether rejuvenation and 

 the beginning of a new cycle of life are impossible. In man and higher 

 mammalians death seems to be caused directly or indirectly through 

 microorganisms or other injuries to vital organs. The example of cer- 

 tain plants, e.g. the Sequoia in California, shows that certain organisms 

 may live thousands of years. 



I pointed out a few years ago that the egg is a valuable object for 

 the study of this problem. The process of fertilization of the egg is 

 a life-saving act. The mature egg which is not fertilized dies as a rule 

 very quickly under conditions under which the immature or the fertilized 

 egg remains alive. If, e.g., fertilized and unfertilized eggs of the same 

 female of Fundulus (a marine fish) are kept in the same vessel with sea 

 water or distilled water, the fertilized eggs remain all alive and develop, 

 while the unfertilized eggs die in a few hours and become putrid in a 



223 



