THE CHROMOSOMES IN HEREDITY. 



235 



binations in forms having from 2 to 36 chromosomes in the pre- 

 synaptic cells. 



Thus if Bardeleben's estimate of sixteen chromosomes for man 

 (the lowest estimate that has been made) be correct, each indi- 

 vidual is capable of producing 256 different kinds of germ- 

 products with reference to their chromosome combinations, and 

 the numbers of combinations possible in the offspring of a single 

 pair is 256 x 256 or 65,536; while To.ropnctistes, with 36 

 chromosomes, has a possibility of 262,144 and 68,719,476,736 

 different combinations in the gametes of a single individual and the 

 zygotes of a pair respectively. It is this possibility of so great a 

 number of combinations of maternal and paternal chromosomes 

 in the gametes which serves to bring the chromosome-theory 

 into final relation with the known facts of heredity; for Mendel 

 himself followed out the actual combinations of two and three 

 distinctive characters and found them to be inherited indepen- 

 dently of one another and to present a great variety of combina- 

 tions in the second generation. 



The constant size-differences observed in the chromosomes of 

 Brackystola early led me to the suspicion, which, however, a 

 study of spermatogenesis alone could not confirm, that the indi- 

 vidual chromosomes of the reduced series play different roles in 

 development. The confirmation of this surmise appeared later 



