AN ANALYSIS OF THE EFFECT OF SELECTION. 45 
modifiers (7. e., modifiers producing only small effects) will account 
for all these facts, with a single exception. Three families were ob- 
tained from F, plants that must, on the two-factor view, have been 
of the same constitution. These plants were heterozygous for one 
pair of genes only. They produced, in F;, the same type of later 
constant (homozygous) families, but differed slightly in the flowering 
times of the earlier constant families produced. According to Ho- 
shino’s view, if the earlier types differed the later ones should have 
differed in the same direction, because they must have received the 
same ‘‘secondary modifiers.” This objection is not valid, for specific 
modifiers that act only in the presence of certain other genes are well 
known (see especially Bridges, 1916), and are sufficient to account 
for the differences observed. This argument is the only one that 
Hoshino gives to support his conclusion that contamination must 
have occurred. We must then conclude that the case does not furnish 
positive evidence for contamination, since it is explicable without re- 
course to that hypothesis.! 
11. UnspeciFIeD CasE IN SWINE. 
This case is cited by Castle (1916b, p. 215), but no references or 
authorities are given. It appears, however, from the legend under fig- 
ure 93 (opposite p. 139) that the belted character is the one referred to. 
The only data bearing on this case that I have found are presented by 
Spillman (1907), and consist of information supplied largely by prac- 
tical swine-breeders. Spillman himself interpreted the case as one in 
which two factor-pairs are involved. The data also suggest the pos- 
sibility that we are dealing with a case of ‘imperfect dominance”’ simi- 
lar to those in poultry. At best, the data are meager and indefinite. 
12. VARIEGATED PERICARP IN MAIZE. 
The paper of Hayes (1917) referred to above should be studied 
in connection with those of Emerson, particularly his full paper (Emer- 
son, 1917), dealing with the same character. These two workers have 
shown that there is a remarkable series of multiple allelomorphs in 
this case, and Emerson has shown very clearly that some of these 
allelomorphs mutate quite frequently—the only established instance 
of the sort. 
1We are not here directly concerned with Castle’s contention that Hoshino’s results prove 
the effectiveness of selection within a pure line. I can not, however, refrain from a few comments 
on that contention. Castle states (1916a, p. 324), in connection with the differences in flowering- 
time between the offspring of early and late flowering sister-plants: ‘‘ From long experience in 
studies of rats with such small differences as are here indicated I have no hesitation in concluding 
that fluctuating variation of genetic significance is here in evidence.’’ One wonders how ex- 
perience in dealing with differences in pigmentation in rats can give an observer special ability 
in determining by inspection the significance of three-tenths of a day difference in the flowering 
time of peas. With respect to Castle’s calculations from Hoshino’s data, it may be pointed 
out that the greatest favorable difference recorded, 1.27 days, is incorrect, and should read 0.26 
day. In view of the fact that there is no guarantee that the material used was homozygous, 
I have thought it scarcely worth while to recalculate all the differences, or to determine their 
probable errors; but it is certain that the probable error of each difference is of the same order of 
magnitude as the average difference itself, 7. e., about 0.3 day. 
