cenogenesis
n . 新生性变异
新生性变异
cenogenesis n 1 :
introduction during embryonic development of characters or structure not present in the earlier evolutionary history of the strain or species (
such as the addition of the placenta in mammalian evolution ) [
synonym : {
cenogenesis },
{
kenogenesis }, {
caenogenesis }, {
cainogenesis },
{
kainogenesis }] [
ant : {
palingenesis }, {
recapitulation }]
Kenogenesis \
Ken `
o *
gen "
e *
sis \,
n . [
Gr . ?
new E .
genesis .]
(
Biol .)
Modified evolution ,
in which nonprimitive characters make their appearance in consequence of a secondary adaptation of the embryo to the peculiar conditions of its environment ; --
distinguished from {
palingenesis }. [
Written also {
cenogenesis }
and {
c [
ae ]
nogenesis }.]
[
1913 Webster ]
Recapitulation \
Re `
ca *
pit `
u *
la "
tion \
(
r [=
e ]`
k [.
a ]*
p [
i ^]
t "[-
u ]*
l [=
a ]"
sh [
u ^]
n ),
n . [
LL .
recapitulatio :
cf .
F .
recapitulation .]
1 .
The act of recapitulating ;
a summary ,
or concise statement or enumeration ,
of the principal points ,
facts ,
or statements ,
in a preceding discourse ,
argument ,
or essay .
[
1913 Webster ]
2 . (
Zool .)
That process of development of the individual organism from the embryonic stage onward ,
which displays a parallel between the development of an individual animal (
ontogeny )
and the historical evolution of the species (
phylogeny ).
Some authors recognize two types of recapitulation , {
palingenesis },
in which the truly ancestral characters conserved by heredity are reproduced during development ;
and {
cenogenesis } ({
kenogenesis }
or {
coenogenesis }),
the mode of individual development in which alterations in the development process have changed the original process of recapitulation and obscured the evolutionary pathway .
[
PJC ]
This parallel is explained by the theory of evolution ,
according to which ,
in the words of Sidgwick , "
the developmental history of the individual appears to be a short and simplified repetition ,
or in a certain sense a recapitulation ,
of the course of development of the species ."
Examples of recapitulation may be found in the embryological development of all vertebrates .
Thus the frog develops through stages in which the embryo just before hatching is very fish -
like ,
after hatching becomes a tadpole which exhibits many newt -
like characters ;
and finally reaches the permanent frog stage .
This accords with the comparative rank of the fish ,
newt and frog groups in classification ;
and also with the succession appearance of these groups .
Man ,
as the highest animal ,
exhibits most completely these phenomena .
In the earliest stages the human embryo is indistinguishable from that of any other creature .
A little later the cephalic region shows gill -
slits ,
like those which in a shark are a permanent feature ,
and the heart is two -
chambered or fish -
like .
Further development closes the gill -
slits ,
and the heart changes to the reptilian type .
Here the reptiles stop ,
while birds and mammals advance further ;
but the human embryo in its progress to the higher type recapitulates and leaves features characteristic of lower mammalian forms --
for instance ,
a distinct and comparatively long tail exists .
Most of these changes are completed before the embryo is six weeks old ,
but some traces of primitive and obsolete structures persist throughout life as "
vestiges "
or "
rudimentary organs ,"
and others appear after birth in infancy ,
as the well -
known tendency of babies to turn their feet sideways and inward ,
and to use their toes and feet as grasping organs ,
after the manner of monkeys .
This recapitulation of ancestral characters in ontogeny is not complete ,
however ,
for not all the stages are reproduced in every case ,
so far as can be perceived ;
and it is irregular and complicated in various ways among others by the inheritance of acquired characters .
The most special students of it ,
as Haeckel ,
Fritz M ["
u ]
tter ,
Hyatt ,
Balfour ,
etc .,
distinguish two sorts of recapitulation {
palingenesis },
exemplified in amphibian larvae and {
coenogenesis },
the last manifested most completely in the metamorphoses of insects .
Palingenesis is recapitulation without any fundamental changes due to the later modification of the primitive method of development ,
while in coenogenesis ,
the mode of development has suffered alterations which obscure the original process of recapitulation ,
or support it entirely .
--
Encyclopedia Americana ,
1961 .
[
PJC ]
cenogenesis \
cen `
o *
gen "
e *
sis \
n . [
Gr . ?
new E .
genesis .]
(
Biol .)
The introduction during embryonic development of characters or structure not present in the earlier evolutionary history of the strain or species (
as addition of the placenta in mammalian evolution );
a modified evolution ,
in which nonprimitive characters make their appearance in consequence of a secondary adaptation of the embryo to the peculiar conditions of its environment ; --
distinguished from {
palingenesis }. [
Also spelled {
caenogenesis }
and formerly {
kenogenesis }.]
[
WordNet 1 .
5 1913 Webster ]
安装中文字典英文字典查询工具!
中文字典英文字典工具:
复制到剪贴板
英文字典中文字典相关资料:
Microsoft – AI, Cloud, Productivity, Computing, Gaming Apps Explore Microsoft products and services and support for your home or business Shop Microsoft 365, Copilot, Teams, Xbox, Windows, Azure, Surface and more
Office 365 login Collaborate for free with online versions of Microsoft Word, PowerPoint, Excel, and OneNote Save documents, spreadsheets, and presentations online, in OneDrive
Microsoft account | Sign In or Create Your Account Today – Microsoft Get access to free online versions of Outlook, Word, Excel, and PowerPoint
Microsofts stock closes worst quarter since 2008 financial crisis - CNBC Microsoft just closed out its worst quarter on Wall Street since the 2008 financial crisis, as investors soured on the software giant's prospects in artificial intelligence The company's stock
Microsoft (MSFT) Stock Price Overview A detailed overview of Microsoft Corporation (MSFT) stock, including real-time price, chart, key statistics, news, and more
Microsoft Corporation (MSFT) - Yahoo Finance Get the latest Microsoft Corporation (MSFT) stock news and headlines to help you in your trading and investing decisions
My Account Access and manage your Microsoft account, subscriptions, and settings all in one place
Sign in to your account - myaccount. microsoft. com Sign in to manage your Microsoft account settings and access personalized services
Microsoft Office Locations | About Microsoft Learn about Microsoft headquarters in Redmond, WA and our offices, locations, and experience centers across the United States
Microsoft Support Microsoft Support is here to help you with Microsoft products Find how-to articles, videos, and training for Microsoft Copilot, Microsoft 365, Windows 11, Surface, and more