80 Some Recent Work on Hybrids in Plants . 
(Torrens calls Mendel’s law (De Vries’ “loi de disjonction.”) Slightly 
modified from Correns it may be stated thus—in respect of certain 
pairs of parental characters the hybrids produce gametes which 
contain between them all possible combinations, in equal numbers, 
of these characters, with the exception that no two characters of 
a pair occur together. 
That Mendel’s law is of the greatest importance in relation to 
the general laws of heredity and to our conception of the relation 
of characters in the organism there can be no doubt. Instead of 
the old idea of the necessary mixing of characters on hybridisation, 
held so strongly by most of the early workers on hybrids, we get a 
new view, as Bateson (’ 01 ) has pointed out, “that a living organism is a 
complex of characters of which some at least are dissociable 
and capable of being replaced by others. We thus reach the 
conception of unit characters which may be rearranged in the 
formation of the reproductive cells.” 
However great the importance of Mendel’s law, there can be no 
doubt that the view formerly put forward by De Vries(’ 00 a,b) that this 
law and that of dominance holds good for nearly all hybrids is 
erroneous. The work of Gartner and Kolreuter shows clearly that the 
law of dominance does not hold for a number of hybrids and Mendel 
himself recognised that it did not hold even for all the characters 
of Pea races. That Mendel’s law has striking exceptions was 
shown by Mendel (’ 70 ) himself in his preliminary studies of Hieracium 
hybrids, in which the characters investigated obey neither the law 
of dominance nor do they separate in the sexual cells, for in the 
second generation all the offspring were found to be like their parents. 
How far Mendel’s law will apply to other cases of hybrids is 
still an open question, but in this connection mention must be made 
of the work done by Correns, De Vries and Tschermak, and the 
recent criticism of Weldon (’ 02 ) on the generality of the law. 
(To be continued.) 
