THE EVOLUTION OF LIVING BEINGS. 57 



of the hybrid, the other kind being identical in con- 

 stitution with the gametes produced by the other 

 parent. 



This of course teaches us nothing, as to the constitu- 

 tion of the gametes; it looks as if the two mated game- 

 tes remain side by side in the zygote, and form, lin- 

 ked hand in hand so to speak, the hybrid, to say good 

 bye to one another, as soon as the vegetative develop- 

 ment of the hybrid comes at an end and it proceeds to 

 form gametes itself. 



Cytology however teaches us that there is not such 

 a loose linkage between the gametes in the zygote, as 

 we would have to accept on the ground of this expla- 

 nation, but that, on the contrary, a very intimate fu- 

 sion of the bodies and even of the nuclei of these ga- 

 metes takes place, in which their individuality, so 

 far as we can see, gets lost with the exception only of 

 the individuality of the chromosomes. 



As the gametes evidently regain their individuality 

 as the hybrid proceeds to form gametes, these latter 

 being identical to those, united in the zygote, from 

 which the hybrid arose, it looks as if the supposition 

 of a loose linkage of the gametes in the zygote were 

 after all correct and that, even during fusion, their in- 

 dividuality could be upheld unimpaired by their chro- 

 mosomes, retaining their individuality. 



But there is some uncertainty — and this must not 

 be overlooked, in the assignement of such exclusive 

 importance to the role of the chromosomes, as this in- 

 terpretation implies — because it is founded on themere 

 supposition that the essence of the individuality of a 



