viii PREFACE 



of animals and that we do not know how they have evolved nor 

 how they are interrelated. It is possible that they might have 

 evolved quite independently from discrete and separate sources. 

 There are only a limited number of chemical elements that are 

 capable of forming stable polymerisation compounds and it is not 

 at all surprising that the same compounds have been formed on 

 several occasions. Quite complex materials such as carbohydrates, 

 peptides and even nucleic acids can be formed by irradiating water 

 containing simple salts and gases. 



It may be suggested that the problem we are examining here, 

 namely that of the evolution and interrelationship of the basic 

 living stocks is a major problem and one that will test the strength 

 and ability of many hundreds of research workers. If this book 

 merely indicates to some of the readers that certain lines of thought 

 are still open to examination, then I shall consider that it has done 

 its allotted task. 



There is, however, a second point that I should like to make, and 

 this concerns not factual material but an attitude of mind. It is 

 very depressing to find that many subjects are becoming encased 

 in scientific dogmatism. The basic information is frequently over- 

 looked or ignored and opinions become repeated so often and so 

 loudly that they take on the tone of Laws. Although it does take a 

 considerable amount of time, it is essential that the basic informa- 

 tion is frequently re-examined and the conclusions analysed. 

 From time to time one must stop and attempt to think things out 

 for oneself instead of just accepting the most widely quoted 

 viewpoint. I have dealt with this attitude in the introductory 

 chapter of this book, though I hope that the moral does not end 

 there but instead runs through the rest of the book as well. 



It is a pleasure to acknowledge the kind help and assistance 

 that various colleagues have given me during the writing of this 

 work. Many of them have read through parts of the book or 

 offered advice on various points. I have profited greatly from their 

 counsel, though of course I bear full responsibility for all the 

 statements and errors. In particular I should like to thank 

 Professor E. Baldwin, Drs. M. S. Laverack, K. A. Munday, 

 S. Smith, Miss D. Wisden, Messrs. Robert Walker, Edward 

 Munn, and Richard Solly for their help and forbearance. 



