214 GENERAL BIOLOGY 



be highly modified by very slight changes in the 

 germinal substance brought about by such unequal 

 cleavage. Furthermore, it is believed by many 

 that there is an individuality of the chromosomes, 

 such that it is not a matter of indifference in what 

 position they may lie in the conjugation known as 

 synapsis, which occurs just before reducing division 

 of maturation. It has been shown that if the 

 chromosomes are all qualitatively different, then 

 the following relations hold : If there are two 

 chromosomes in the somatic cell and hence but one 

 in the reduced gametes, there are two possible com- 

 binations in the gametes and four in the zygotes ; 

 if there are eight in the somatic cells, there will be 

 16 possible combinations in the gametes and 256 

 in the zygotes ; if 16 in the somatic cells, then there 

 will be 65,536 possible combinations in the zygote; 

 if 32 in the somatic cells, there may be over L2!)k- 

 467,296 possibilities in the zygotes. It would seem, 

 therefore, that on a basis of chance alone abundant 

 opportunity for blastogenic variation is afforded by 

 the mechanism by which the reduction and subse- 

 quent recombination of chromosomes is brought 

 about in maturation and zygosis. 



HEREDITY 



Heredity and Inheritance. All living creatures, 

 as we have seen, are descended from ancestors 

 which they resemble more or less closely. The facts 

 of variation teach us that the resemblance is never 

 an actual duplication, yet all organisms " conform to 



