EFFECTS OF AMPHIMIXIS ON THE GERM-PLASM 249 



idant were doubled before the division, ten combinations would 

 be possible. This means that one individual of any species 

 possessing four idants in each of its cells can produce ten kinds 

 of ova and spermatozoa differing from one another as regards 

 individual hereditary tendencies. Two new idants are added to 

 such an ovum when one of them is fertilised by the spermatozoon 

 of another individual ; and since each parent produces ten 

 different kinds of germ-cells, as many offspring differing in 

 character from one another may arise from these two parents as 

 there are possible combinations of the ten kinds of spermatozoa 

 of the father with the ten kinds of egg-cells of the mother, i.e.y 

 ID X 10 = 100. 



With eight idants, 70 combinations are possible without, and 

 266 with, doubling ; and following this up, twelve idants will 

 thus give 924, or 8,074 combinations ; sixteen, 12,870, or 258,570 ; 

 twenty idants, 184,756, or 8,533,660; and with thirty-two idants, 

 about five hundred times as many combinations would be 

 obtained with doubling as without it. 



Since the same number of idants from each of the conjugating 

 cells come together in the process of fertilisation, and each of 

 the parental germ-cells only contains one of the many possible 

 combinations of idants, the number of variations in the germ- 

 plasm which it is possible for two parents to produce must be an 

 enormous one. It can be calculated by multiplying the number 

 of possible combinations in the two conjugating cells together : 

 thus in the case of twelve idants only, it would amount to 8,074 

 X 8,074. Unfortunately we are unacquainted with the number 

 of idants in the human subject, in which we are best able to 

 recognise individual differences in most minute detail. We may, 

 however, suppose that this number is more than four. If, for 

 instance, it were as high as twelve, we need not wonder that 

 two children born consecutively are never identical, as must be 

 the case if they had originated from the same combination of ids 

 of the germ-plasm. Approximately identical children only occur 

 in the case of twins, and we have every reason to believe that 

 these originate from one sperm-cell and one ovum. 



We cannot as yet judge with certainty as to how far the entire 

 idants pass unchanged as regards their constituent ids from the 

 germ-cells of one generation into those of the next. The phenom- 

 ena of the reduction in the germ-cells which have recently been 

 made known to us in the case of various Arthropods by the re- 



