IN THE TROPICS. 
323 
more complicated phenomena were observed. And the 
same was the case in the poultry crosses studied by Bateson 
( 6 ). 
Mendelian ratios have been observed in the case of certain 
crosses between different races of mice by Cuénot (24) and 
Dar bishire (27). Here again phenomena other than those 
seen by Mendel in peas appear in certain instances to 
complicate the result. Bateson (5) has summed up the infor¬ 
mation existing as regards colour-heredity in mice and rats, 
and has shown that Mendel’s theory throws abundant light 
upon the earlier results of Crampe and von Guiata. The 
more recent results of Cuénot are discussed below. 
De Vries in his earlier papers ( e.g ., 67 ), was disposed to 
assert an almost universal scope for Mendel’s Law and also 
for the law of dominance, except in cases of what he calls 
“false hybridism,” a term which de Vries used in a wider 
sense than Millardet. But Correns (15) and Tschermak 
(59) have found exceptions to both laws in the inter-race 
hybrids which they have studied. These two authors have 
shown, however, that the law of segregation of characters in 
the gametes in equal numbers has a very wide scope. 
Tschermak (59) finds no part of Mendel’s discovery to 
apply universally even to peas. Some of this writer’s 
earlier criticisms have, however, since been explained away, 
especially those which had reference to the phenomenon of 
segregation of characters. Tschermak found blending 
instead of dominance in the case of a considerable number 
of pairs of characters, including some of those for which 
Mendel described a regular occurrence of dominance in his 
own experiments. But he found blending to be more 
common in vegetative than in cotyledon characters. 
Weldon (76) has criticized Mendel’s original work. He 
cited a number of exceptions to dominance, but failed to 
notice sufficiently the importance of Mendel’s Law ; and 
Mendel’s own demonstration of this principle by re-crossing 
with the recessive form. 
