330 
case of the cretin may eventually throw light upon this point 
when the System on which N and F are coupled shaü have been 
determined. 
The question now arises how these gametic Systems are 
formed. In each the characteristic phenomenon is that the hete- 
rozygote produces a comparatively large number of gametes 
representing the parental combinations of factors and comparatively 
few representing the other combinations. In describing the original 
case of coupling, namely that between blue colour and long poUen 
in the sweet pea, we pointed ont that no simple System of 
dichotomies could bring about these numbers, and also that it 
was scarcely possible that such a series could be constituted in 
the process of gameto-genesis of a plant in whatever manner the 
divisions took place. In saying this regard was of course had 
especially to the female side, and this deduction has become 
more clear in view of the fact that we now know a series con- 
sisting of 256 terms. It is practically certain that the ovules 
derived from one flower of the sweet pea, even if all collateral 
cells be included, cannot possibly be arranged in groups of this 
magnitude. A pod rarely contains more than 9 or 10 good seeds 
at the most, so that even if we reckon 12 potential seeds to the 
pod and 8 potential gametic cells to the ovule the total is still 
only 96, which is much too few. Nevertheless our series of numbers 
is plainly a consequence of some geometrically ordered series 
of divisions. 
There is evidence also from other sources that segregation 
may occur earlier than gameto-genesis. Miss Saunders' observations 
on M a 1 1 h i o 1 a ^) and on P e t u n i a ^) proved that in those plants 
the factors for singleness are not similarly distributed in the male 
and female cells. The recent work of de Vries on Oenothera 
b i e n n i s and m u r i c a t a ^) has provided other instances of 
dissimilarity between the factors borne by the male and female 
Organs of the same flower. In all these examples it is almost 
certain that segregation cannot take place later than the formation 
of the rudiments of the carpels and of the stamens respectively. 
The only alternative is that in each sex the missing allelo-morphs 
are represented by some somatic cells of the sexual apparatus, 
1) Rep. Evol. Comm. Roy. Soc. IV, 1908, p. 36. 
2) Journ. genetics, I, 1911. 
ßiol. Centr. Bd. XXXI, 1911, p. 97. 
