ORIGIN OF LIFE, SEX, SPECIES, ETC. 231 



comparatively small variations in either the material 

 or force constituents of the two substances which 

 form the fertilized ovum, or in the structural proper- 

 ties of the organs into and through which they have 

 to pass, or in which they are lodged after the coitus. 



Since innumerable additions of small modifica- 

 tions arising by variation from generation to 

 generation are competent to account for enormous 

 differences in somatic structures, how can a rational 

 person doubt that they are able to produce small 

 differences sufficient to prevent perfect co-operation 

 in either one or both of the substances which form 

 the fertilized ovum? Or why should such small 

 differences not result in modifications of the repro- 

 ductive organs sufficient to interfere with perfect 

 accommodation of one of the component substances 

 or of the fertilized ovum? In either case, failure to 

 reproduce or a defective reproduct, such as sterile 

 offspring, might be the result. 



The occasional occurrence of barrenness evidences 

 that variations sufficient to make reproduction im- 

 possible between those of the same species hap- 

 pen not infrequently. Scientific literature seems a 

 blank w T ith reference to these questions: Could an 

 individual barren with reference to the normal type 

 successfully reproduce if mated with a specimen 

 similarly barren, but whose barrenness is caused by 

 modifications in reproductive cells or organs which 

 make these cells or organs complementary to repro- 

 ductive cells or organs modified in the same man- 



