268 THE ORCHID REVIEW. [SEPTEMBER, 1914 
originate new cells, and that each nucleus contains a definite number of 
bodies, called chromosomes, which are believed to be the bearers of 
‘hereditary qualities. The particular kind of division seen in reproductive 
cells takes the form of halving the number of chromosomes, and this is 
technically known as the reduction division, and is accompanied by the 
peculiar property that these reduced cells are incapable of proceeding 
further until after a sexual process has taken place. These specialised cells 
are of two kinds, male and female, and occupy a different position with 
regard to the parent organism, but they are identical in their origin and 
method of development, and contain the same number of chromosomes. 
Their union by the sexual process restores the original number of 
chromosomes, and gives the stimulus -to further development and the 
production of a new individual. 
‘This new individual develops in accordance with the characters of the 
two reproductive cells which unite to give it birth, but it is in the earlier 
reduction division that the distribution of these characters among the 
individual reproductive cells takes place. This gives us an insight into the 
different behaviour of species and hybrids with respect to their offspring. 
The mosaic character, so far as it exists, prevents uniformity in the 
‘composition of the reproductive cells. It is due to incompatability between 
characters of diverse origin, and results in the diversity seen among 
secondary hybrids from the same seed pod. And it is not universal, for 
‘some hybrids reproduce themselves true from seed. In such cases, to use 
the language of Mendel, the differences are “ entirely and permanently 
accommodated together” (the italics are his). The compromise, which 1s 
always necessary in the union of diverse elements and often only temporary, 
is here complete and permanent. Herein lies the difference between 
mosaic and blendid inheritance, and the measure of the difference ® 
incompatability. 
Blended inheritance results in intermediate hybrids, or in characters 
that are intermediate between those of their parents. Mosaic inheritance 
is common in a mixed population, such as that created by the hybridist 
and it was the peculiar behaviour of hybrids that led to Mendel’s origina 
experiments, as may be seen by an extract from the introduction t? e 
celebrated paper: ‘‘ The striking regularity with which the same hybr! 
forms always reappeared whenever fertilisation took place between o 
same species induced further experiments to be undertaken, the object © 
which was to follow up the developments of the hybrids in their progeny: 
To this object numerous careful observers, such as KOlreuter, Ga 
Herbert, Lecoq, Wichura, and others, have devoted a part of their lives 
with inexhaustible perseverance. . . . That, so far, no genet A 
applicable law governing the formation and development of hybrids as a 
