Ewartr— Variation: Germinal and Environmental. Sk 
representing remote as well as intermediate stages in the ancestral history. 
Judging by the results, one of the immediate ancestors may control the develop- 
ment, or the control may be about equally divided between immediate, inter- 
mediate, and remote ancestors, the issue, as in many battles, being decided by 
the quality, individuality, or character (what we call the prepotency) of the 
successful groups of vital units, rather than by their numbers. 
The combmed results of germinal and environmental variation. 
As variation is intimately associated with intercrossing, the best way to 
illustrate the combined results of germinal variation and the variation in the 
germ-plasm due to food, temperature, &c., 7.e. environmental variation, will 
be to give the results of a number of intercrossing and interbreeding 
experiments. 
It may be said that intercrossing only differs from ordinary cross-fertilization, 
in that the results appear in larger type, are, as it were, magnified. ‘This is true 
of intercrossing between closely allied races, but not of intercrossing between 
distinct varieties, and still less between different species. In the latter there is, 
to use the same simile, a difference in the character as well as in the size of the 
letters, in most cases a reversion to simpler and more primeeval forms. When for 
several generations, the ancestors have been intimately related and almost identical 
in characters, the offspring, as a rule, resemble the parents, doubtless, because the 
vital units or groups of units proceeding from both parents have all very similar 
tendencies. 
Whether, when the parents have been living under very different conditions, 
and differ in age, vigour, &c., variability (environmental variation) shows itself in 
the offspring, has not yet been systematically investigated. 
The following are some of the more striking results of intercrossing :— 
1. The offspring may, down to the remotest details, be all but intermediate 
between the two parents. Examples of this intermediate condition, though 
not very common, certainly occur. In a cross between black and white birds, 
black and white feathers may alternate with each other, over a considerable part, 
if not over the whole body. ‘This once happened in a cross-bred pigeon, and the 
same thing happens in plants, in e.g. a cross between two species of the tobacco 
plant, Micotiana rustica and N. paniculata.* 
In such cases it may be presumed that equally nourished, equally matured, and 
equally prepotent germ-cells meet and blend in such a way that both parents are 
* Kollreutter, ‘‘ Vorlaufige Nachricht yon einigen das Geschlecht der Pflanzen betreffenden Versuchen 
und Beobachtungen,” 1716. 
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