Ewart— Variation: Germinal and Environmental. 369 
individual eventually developed will be readily admitted. Were it possible to 
measure accurately the potential variability of two germ-cells before conjugation, 
there are good reasons for believing that, owing to inequalities of nutrition, 
assimilation, &c., the ovum, independently of the ‘reducing division,” would be 
different morphologically from the ovisperm, out of which the female parent was 
developed, as the sperm would differ from the ovisperm which gave rise to the 
male parent. Moreover, the two germ-cells would differ physiologically, in e.g. 
their ripeness and vigour as a whole, and in the ripeness, vigour, &c., of some of 
the groups of vital units, ancestral protoplasm being prepotent in some groups, 
specific or racial protoplasm in others. The result of these various differences, 
would be that the new individual, when developed, would not in its characters 
assume the intermediate position which an estimate of the structure of the two 
germ-cells might have led us to anticipate. 
In other words, there are excellent reasons for supposing that though 
amphimixis is not a cause of variation, it consists in something more than the 
mere mechanical blending of what might be known as the structural variations of 
the two germ-cells. When a paper-maker introduces two kinds of pulp into one 
end of his machine, he knows to a nicety the kind of paper that will stream off at 
the other end. When, however, the eggs of one variety of fish are fertilized by 
the milt of a different variety, the pisciculturalist is unable to predict the exact 
form, colour, &c., of the fish which will eventually appear in his hatching boxes. 
In the same way, a breeder, when he crosses, say, a piebald mare, with two 
apparently identical bay ponies, may obtain a bay foal the one year, a piebald 
foal the next. 
Having failed to find any experimental evidence of the transmission of 
acquired specific variations, and having given reasons for the belief that the germ- 
cells differ from each other in their nutrition, ripeness, &c., and that the ova are 
especially liable to change after the escape of the second polar body, I may now 
attempt to indicate how the differences in the germ-cells count in shaping the 
destiny of the new individual. 
At the beginning of a campaign, or, for that matter, of a modern battle spread 
over a wide area, it is impossible, or at least unwise, to predict what the final 
issue will be, even when a fairly accurate estimate of the resources of the two 
combatants is available, and allowance is made for the physical conditions under 
which the operations are conducted. In the same way, it is impossible, and ever 
will remain impossible, to predict what will be the result of the union of two germ- 
cells, even when the ancestral history is well known, and when the parents have 
been living from their birth under similar conditions. 
When the male and female germ-cells meet, a whole series of campaigns is 
entered on with ever varying results. 
TRANS, ROY. DUB. SOC., N.S., VOL. VIJ., PART XIII. 3F 
