【医】 世代交替

Generation \Gen`er*a"tion\, n. [OE. generacioun, F.
g['e]n['e]ration, fr.L. generatio.]
1. The act of generating or begetting; procreation, as of
animals.

2. Origination by some process, mathematical, chemical, or
vital; production; formation; as, the generation of
sounds, of gases, of curves, etc.

3. That which is generated or brought forth; progeny;
offspiring.

4. A single step or stage in the succession of natural
descent; a rank or remove in genealogy. Hence: The body of
those who are of the same genealogical rank or remove from
an ancestor; the mass of beings living at one period;
also, the average lifetime of man, or the ordinary period
of time at which one rank follows another, or father is
succeeded by child, usually assumed to be one third of a
century; an age.

This is the book of the generations of Adam. --Gen.
v. 1.

Ye shall remain there [in Babylon] many years, and
for a long season, namely, seven generations.
--Baruch vi.
3.

All generations and ages of the Christian church.
--Hooker.

5. Race; kind; family; breed; stock.

Thy mother's of my generation; what's she, if I be a
dog? --Shak.

6. (Geom.) The formation or production of any geometrical
magnitude, as a line, a surface, a solid, by the motion,
in accordance with a mathematical law, of a point or a
magnitude; as, the generation of a line or curve by the
motion of a point, of a surface by a line, a sphere by a
semicircle, etc.

7. (Biol.) The aggregate of the functions and phenomene which
attend reproduction.

Note: There are four modes of generation in the animal
kingdom: scissiparity or by fissiparous generation,
gemmiparity or by budding, germiparity or by germs, and
oviparity or by ova.

{Alternate generation} (Biol.), alternation of sexual with
asexual generation, in which the products of one process
differ from those of the other, -- a form of reproduction
common both to animal and vegetable organisms. In the
simplest form, the organism arising from sexual generation
produces offspiring unlike itself, agamogenetically.
These, however, in time acquire reproductive organs, and
from their impregnated germs the original parent form is
reproduced. In more complicated cases, the first series of
organisms produced agamogenetically may give rise to
others by a like process, and these in turn to still other
generations. Ultimately, however, a generation is formed
which develops sexual organs, and the original form is
reproduced.

{Spontaneous generation} (Biol.), the fancied production of
living organisms without previously existing parents from
inorganic matter, or from decomposing organic matter, a
notion which at one time had many supporters; abiogenesis.


Alternate \Al*ter"nate\ (?; 277), a. [L. alternatus, p. p. of
alternate, fr. alternus. See {Altern}, {Alter}.]
1. Being or succeeding by turns; one following the other in
succession of time or place; by turns first one and then
the other; hence, reciprocal.

And bid alternate passions fall and rise. --Pope.

2. Designating the members in a series, which regularly
intervene between the members of another series, as the
odd or even numbers of the numerals; every other; every
second; as, the alternate members 1, 3, 5, 7, etc.; read
every alternate line.

3. (Bot.) Distributed, as leaves, singly at different heights
of the stem, and at equal intervals as respects angular
divergence. --Gray.

{Alternate alligation}. See {Alligation}.

{Alternate angles} (Geom.), the internal and angles made by
two lines with a third, on opposite sides of it. It the
parallels AB, CD, are cut by the line EF, the angles AGH,
GHD, as also the angles BGH and GHC, are called alternate
angles.

{Alternate generation}. (Biol.) See under {Generation}.