CHAPTER XIV. 



ORIGIN AND SIGNIFICANCE OF SEX. 



In order to understand the nature of sex, let us 

 return to the consideration of the processes of life 

 among unicellular organisms. In the first place, 

 we see that those constructive changes of the pro- 

 toplasm which are caused by the environment are 

 not destroyed when the protoplasm divides into 

 two parts. The elementary nervous organisation 

 remains effective in each of the two parts. The 

 results of the original stimuli acting upon the single 

 mass are shown in the development of each part, 

 as the magnetising of a steel bar will cause each 

 piece of the bar, when broken, to form a magnet. 

 What the nature of these changes in the protoplasm 

 may be, from a physical point of view, we cannot 

 conjecture. We have seen that they are not 

 destroyed by a division of the protoplasm, and we 

 have further to notice that they are not destroyed 

 when two separate bits of protoplasm unite and 

 fuse together in one mass. Here the illustration 



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