YUZO HOSHINO 275 
aAbE, same as F^). From the results of the raising of F^ offsprings of those 
F3 families such as No. 4 and No 5 of Table 20 which could be assumed, from 
their parent classes and their variation types, not to be descendants of F^ 
having the same zygotic constitution as (aAbB), we should expect variation 
types of monohybrid segregation only. In the actual F^^ raisings, however, 
this expectation was not fulfilled. In Table 21, the variation types in B sug- 
gest those of monohybrid segregation, but those in A are too complicated 
to be regarded as monohybrid segregation. 
Then, by assuming the three-factor hypothesis, can these facts be ex- 
plained ? Although our experiments were conducted on too small a scale 
to supply enough material for a discussion of this subject, so far as our ex- 
periments go, the three-factor hypothesis does not conflict with actual results. 
As we have noted above, among 340 F^ individuals (Table 19), 5 which shot 
forth during the two days 88 and 89, might be taken as the early constants 
and 4 which shot forth within the variation range of the late parent, as the 
late constants. These numbers of both early and late constant Fg individuals 
are in admirable correspondence with the calculated number 5.3 (340/64), 
according to the three-factor hypothesis. The variation types of A and 3 i'l 
Table 21, which were not conceivable on the two-fiictor hypothesis, are quite 
acceptable on the three-factor hypothesis, when we take F2 grand-parent of 
B as monohybrid such as aabBcC, aabbcC> or aAbbcc, (see foot notes on 
page 264), and that of A, as a dihybrid such as aabBcC, aAbbcC or aAbBcC. 
Here we wish to propose the three-factor hypothesis for the interpreta- 
tion of the inheritance of the shooting character in the rice varieties which 
we have used in our present work. 
Owing to climatic conditions in Sapporo, experiments on a sufficiently 
large scale were not possible by the author, but he liopes at some future date, 
with the co-operation of some investigator in southern Japan, to obtain more 
conclusive results. 
