58 THE EVOLUTION OF LIVING BEINGS. 



gamete lies in its chromosomes, while the only reason 

 we have for this supposition is, that we can make these 

 chromosomes visible and observe their behaviour du- 

 ring nuclear fusion and mitosis. 



It must however not be forgotten, that there may 

 be f. i. in the cytoplasm of the fusing gametes parti- 

 cles wich retain their individuality, just as well as the 

 chromosomes do, butwhose behaviour remains intraca- 

 ble to us, because we lack the means to make them 

 visible. 



If such particles did exist, it would of course be inad- 

 missable to ascribe to the chromosomes the exclusive 

 abihty to uphold the individuality of the gametes. 



Yet — taken, all in all, we know of chromosomes 

 especially the fact, that where gametes differ greatly 

 in size, the quantity of cytoplasm introduced by the 

 male gamete, is insignificantly small compared to that 

 of the ovum, and yet reciprocal crosses frequently 

 give the same result — there is certainly good reason 

 to consider the chromosomes to be very important 

 constituents of the gametes, so that there is nothing 

 against the supposition that they are able to maintain 

 the individuaUty of the gametes, even during their 

 fusion in the zygote. 



And with this retention of the individuality of the 

 gametes through their chromosomes, the production 

 by the hybrid of a number of gametes, half of which is 

 identical with the gametes of the one, half of which is 

 identical with the gametes of the other parent, is in full 

 accord. 



As soon however, as we proceed to mate gametes de- 



