NATURAL VARIATIONS 137 



playing on the development of the zygote can ne#er 

 exactly repeat themselves. To mention one point alone, 

 the relative " ages " of a fusing ovum and spermatozoon 

 must be variable, and their respective powers of future 

 restoration might easily be affected by an early fusion or 

 the reverse. Again, the place of implantation in the maternal 

 uterus varies, and the uterus as an environment for foetal 

 development must vary with maternal health and age. 

 During gestation the blood of the mother, which nourishes 

 the foetus, must vary with the health, the habits, and the 

 general environment of the mother, and these factors can 

 never be the same in successive pregnancies. On the whole, 

 it may well be that the variation of successive offspring is 

 partly natural and partly acquired. 



With respect to the plan of the Individual body, this, 

 for the given sex, is always fundamentally the same, though 

 capable of showing endless variation in the matter of detail. 

 The male and female sexual element " plans " being, re- 

 spectively, fundamentally always the same, it is not sur- 

 prising that accidental resemblances between Individuals 

 of widely separated stocks are often recognisable. The 

 potential variations of the male or female element " plan " 

 must be limited in number ; but the number will be 

 inconceivably huge, depending as it must on the ultimate 

 particulate constitution of the basoplasm, and the endless 

 varieties of modifying force and its mode of application. It 

 follows, then, that when the two elements unite, the possible 

 somatic variation of the resulting growth-cycle has, as it 

 were, no limits. Thus, no Individual is ever exactly repro- 

 duced or repeated, though many characters may re-exhibit 

 themselves in the offspring. 



Evolution, as we have seen, can be regarded as the 

 evolution of Continuity by multiple progression. The body 

 is a multiple of single cells. The ovum, a single " cell," 

 is a multiple of its plasmolecules ; the plasmolecule is a 

 multiple of its atoms, and so on. And as one female is 

 fundamentally the same as another, so is one ovum funda- 

 mentally the same as another ; differences between females 

 are essentially matters of detail, and the same may logically 

 be concluded with respect to ova. We can only guess at 

 what these matters of detail may be in the case of ova ; 



