CAUSES OF VARIATION 



liability to internal change and not at all, as is erroneously sup- 

 posed, for the inheritance of acquired characters, because the 

 characters in question were not "acquired" in the ordinary 

 acceptance of the term, they were the result of internal, not 

 external, impulses. 



SECTION V INFLUENCE OF THE CONDITION OF THE 

 GERM UPON DEVELOPMENT 



Staleness. Both the male and the female germ cells are 

 capable of living for a considerable time after maturation, so 

 that fertilization may be somewhat delayed ; how long is not 

 known, and what the effect of delay may be is not fully 

 understood. 



Experiments by Vernon upon the ova and spermatozoa of the 

 sea urchin of different ages, from nine to forty-five hours, indicate 

 that the size of the larva is in some degree dependent upon the 

 freshness of the germ at fertilization. 1 The results of a number 

 of trials were as follows : 



1 . With stale ova and stale sperm the resulting larvae differed 

 but slightly from the normal (in which both were fresh). 



2. With fresh ova and stale sperm the larvae were distinctly 

 larger (5.8 per cent). 



3. With stale ova and fresh sperm the larvae were distinctly 

 smaller than when both were fresh (4.9 per cent). 



It is certain that the above combinations as to staleness are 

 possible in the fertilization of mammals by mating and of plants 

 by pollination. Whether the results are the same and whether 

 the differences persist through life are, of course, unknown. The 

 facts recorded are suggestive, but whether they will ever be 

 useful remains to be determined. 



Individuality of the germ. That successive germ cells from 

 the same individual may be substantially different, even aside 

 from considerations of maturation, is a fact beyond question. 

 The ear of corn, like its tassel, matures from the base upward. 

 The tip kernels are not only younger but decidedly smaller than 

 their half-sisters at the base. The different peas in a pod are 



1 Vernon, Variation in Animals and Plants, pp. 105-108. 



