BASIC ASSUMPTIONS 13 



possible that a more detailed examination of mitosis will show that 

 it too is a polyphyletic system devised for the successful separation 

 of the nuclear material into two equal sets. Whether one could go 

 as far as Boyden (1953) and say ,; Under the circumstances the 

 widespread occurrence of what is called mitosis or meiosis is no 

 proof of real genetic relationships of all such organisms. On the 

 contrary the very existence of such mechanisms in organisms 

 otherwise so diverse as Protista, Metazoa, and Metaphyta, is 

 strongly suggestive of convergence and may thus be interpreted 

 with the theory of the strictly polyphyletic origins of the major 

 groups of organisms " is another matter in our present state of 

 ignorance. 



What then can one conclude about the chemical and physical 

 nature of protoplasm? Simply that we have a very great deal to 

 learn about it. Modern developments are making it abundantly 

 clear that some of our previous concepts are quite inadequate and 

 that the picture is very much more complex than previously 

 imagined. It would be a great mistake to assume that all is chaos 

 and that there are no general common systems, but it would be a 

 mistake of equal magnitude to assume that everything is very 

 simple and that but one system will be found in all protoplasm. 

 From our present viewpoint there would appear to be at least four 

 or five different systems which allow a cell to obtain its energy. 

 There are minor variations in this pattern and the higher animals 

 may show less variation than do the bacteria (though few higher 

 animals other than the pigeon and the rat have been studied). 

 The picture in no way allows us to dogmatise and state that life 

 in all its manifestations shows a common biochemical system 

 indicative of a single genesis. The evidence at present does not 

 by any means exclude the concept that present-day living things 

 have many different origins. 



Polyphyletic origin of life 



If we do not hold that the origin of life was unique, i.e. life is 

 monophyletic, there is the alternative point of view. This is that 

 living things have been created many times, i.e. polyphyletic. 



There are two ways of considering the multiple origin of life. 

 The first is to consider that life is continuously being created all 

 the time, i.e. that spontaneous generation is always occurring. The 



