38 PROBLEMS OF EVOLUTION 



of over-complexity, over-specialisation. Death, I hold, became 

 normal, inevitable, through this cause. But it must have been 

 present from the first, quite apart from unfavourable conditions, 

 among the simplest of living organisms as an abnormal occurrence. 

 There must be natural deaths occasionally among bacteria : among 

 these billions of fissions there must be occasional failures. Does 

 not Darwinism depend upon variations favourable and unfavour- 

 able ? And an absolute monstrosity even among bacteria will 

 require no helping out of the world. But what at this low 

 level is rare and abnormal, has become normal among the more 

 complex forms of life. 



Summary I have now tried to find the origin of variation and of death. 

 Of both I regard fission as the primary cause. The nucleus 

 cannot in any case be divided into absolutely equal or similar 

 parts, and, besides this, the antecedent movements involve 

 change ; hence variation. But this inequality may be so great 

 that one of the resultant "halves" may lack some of the vital 

 elements altogether. In this case death must ensue. Conjuga- 

 tion makes good what is lost and so is the corrective of excessive 

 variability, over-specialisation, loss of vital elements, leading in- 

 evitably to death. But since the two uniting organisms are not 

 exactly similar, it must besides restoring vitality lead to new 

 combinations, in fact to variations. 



The strength of heredity is the wonderful phenomenon for 

 which we have to account ; variability results" as a matter of 

 course from the system of reproduction. Heredity can be ex- 

 plained only on the theory of the continuity of the germ-plasm ; 

 it owes its strength to the unintermitted action of Natural 

 Selection which is continually checking wild deviations from 

 specific type. And, having been thus developed, it is liable to 

 fail when selection slackens. 



Some It is worth while now to pause and reflect how much, or how 

 flecdo^s fad e > theories of evolution attempt to explain. They are all 



on evolu- more or less mechanical theories of life, that undertake to tell us 



m how the development of the complex forms from the simple 



came about. We have convincing evidence put before us that 



evolution has taken place and Darwinism supplies us with a good 



