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Ewarr— Variation: Germinal and Environmental. 355 
individual may not be settled, but undoubtedly more occurs than the laying of 
the foundations. Subsequent to conjugation there is considerable scope for 
variation in the size, colour, vigour, &¢c., of the new individual, as there are 
possibilities of various changes of the germ-cells prior to conjugation. All 
the variations in the germ-cells up to the moment of conjugation, together 
with the variations during development and growth, I shall refer to as 
Environmental Variations. 
ENVIRONMENTAL VARIATION. 
I.—During Development. 
It will be convenient first to consider environmental variations beginning with 
those that occur during development. By variation I understand difference in 
structure, habits, &c., between the offspring and their parents. These differences 
may be innate, 7.e. have their roots in the changes in the germ-cells prior to 
conjugation, or they may be acquired after conjugation owing to every individual 
being plastic enough to respond, up to a certain point, to external stimuli. 
Further, these differences, whether germinal or environmental, may be established 
at birth, or they may appear at any period of the life-history, and some of the 
new departures may be handed on to the offspring of a subsequent if not the 
succeeding generation. 
Hitherto it has been usually assumed that all congenital characters are trans- 
mitted to the offspring. But, if by congenital is meant characters pertaining or 
belonging to the individual at birth, this assumption is unwarranted: for, in 
addition to hereditary characters pertaining to the germ-plasm, ¢.e. inherited 
through the male and female germ-cells, and new characters created during 
conjugation, there are various characters acquired during development of a purely 
environmental and not necessarily transmissible nature. 
In certain families a dwarf appears at irregular intervals. We rightly, I 
think, account for the occasional appearance of a dwarf by the principle of 
heredity—it is a case of recurring germinal variation. But all dwarfing is 
not due to hereditary influences; it is sometimes, though congenital, purely 
environmental. It may, ¢.g. be entirely due to an insufficient supply of 
nourishment. 
Some time ago I found in a wild rabbit twelve young, eight in one uterus, 
four in the other. All the eight in the one uterus were of uniform size and quite 
as advanced in their development as the four (also uniform in size) in the other 
uterus, but they were only half the size. When the eight were placed in one 
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