HEREDITY AND SEX 



CHAPTER I 



THE EVOLUTION OF SEX 



ANIMALS and plants living to-day reproduce them- 

 selves in a great variety of ways. With a modicum of 

 ingenuity we can arrange the different ways in series 

 beginning with the simplest and ending with the more 

 complex. In a word, we can construct systems of 

 evolution, and we like to think that these systems reveal 

 to us something about the evolutionary process that 

 has taken place. 



There can be no doubt that our minds are greatly 

 impressed by the construction of a graded series of 

 stages connecting the simpler with the complex. It is 

 true that such a series shows us how the simple forms 

 might conceivably pass by almost insensible (or at 

 least by overlapping) stages to the most complicated 

 forms. This evidence reassures us that a process of 

 evolution could have taken place in the imagined order. 

 But our satisfaction is superficial if we imagine that 

 such a survey gives much insight either into the causal 

 processes that have produced the successive stages, or 

 into the interpretation of these stages after they have 

 been produced. 



Such a series in the present case would culminate 

 in a process of sexual reproduction with males and 



i 



