236 



FOUNDATIONS OF BIOLOGY 



qualitatively distinct. And further that these qualitative 

 differences are the physical basis of inheritance the de- 

 terminers (GENES) of characters which will be realized in the 

 individual or the race to which the cell containing them con- 

 tributes. Such being the case, the chromosomal complex of 

 the nuclei which arises after synapsis that is, the nuclei 



FIG. 127. A, section through the egg of a primitive Vertebrate, the Lamprey. B 

 sperm of the same species, drawn to scale, d.en, dense endoplasm; i.m, inner membrane 

 o.m, outer membrane; p, granular 'polar' cytoplasm; v.en, vacuolated endoplusm 

 T.ex, vacuolated ectoplasm; /, first polar body; II, spindle for second polar body 

 (From Kellicott.) 



of the gametes depends on how the various chromosomes 

 happen to be distributed during the two maturation divisions. 

 As a matter of fact all the chromosomal combinations occur 

 which are mathematically possible with the available num- 

 ber of chromosomes in a given species, but with one limita- 

 tion: every cell must receive one member of each synaptic 

 pair of chromosomes, so that each and every gamete receives a 

 complete simplex group of chromosomes, but rarely the same 



