multiplicity of causes acting
nearly equally in both directions. It is characterized by having more
individuals of a mediocre degree and progressively fewer above and below
this mode.

NUCLEUS (little nut), a central, highly-organized part of every
living cell, which seems to play a directive role in cell-development
and contains, among other things, the chromosomes.

PATENT (lie open), a term applied to traits which are
manifestly represented in the body as well as the germ-plasm of an
individual. The converse of "latent."

PROBABILITY CURVE, the same as normal curve. Also called a
Gaussian curve.

PROTOPLASM (first form), "the physical basis of life"; a
chemical compound or probably an emulsion of numerous compounds. It
contains proteins which differ slightly in many species of organism. It
contains carbon, hydrogen, oxygen, nitrogen, sulphur, and various salts,
but is so complex as to defy exhaustive analysis.

PSYCHIATRY (soul healing), the study of diseases of the mind.

RECESSIVE (draw back), the converse of dominant; applied to one
of a pair of contrasted Mendelian characters which can not appear in the
presence of the other.

REGRESSION (back go), the average variation of one variable for
a unit variation of a correlated variable.

SEGREGATION (aside flock), (1) as used in eugenics means the
policy of isolating feeble-minded and other anti-social individuals from
the normal population into institutions, colonies, etc., where the two
sexes are kept apart. (2) The term is also used technically in genetics,
to refer to the discontinuity of the variation of characteristics
resulting from the independent distribution of factors before or at the
time of formation of the gametes.

SELECTION (apart pick), the choice (for perpetuation by
reproduction) from a mixed population, of the individuals possessing in
common a certain character or a certain degree of some character. Two
kinds of selection may be distinguished: (1) natural selection, in which
choice is made automatically by the failure to reproduce (through death
or some other cause) of the individuals who are not "fit" to pass the
tests of the environment (vitality, disease resistance, speed, success
in mating, or what not); and (2) artificial selection, in which the
choice is made consciously by man, as a livestock breeder.

SEX-LIMITED, a term applied to traits which differ in the two
sexes, because influenced by the hormones of the reproductive gl