effected
..
abruptly by a few
stages;
...OMIT 1869 |
and in a concealed manner; 1866 |
but the transformations are in reality numerous and
gradual, though concealed. gradual, though concealed. 1869 |
graduated. 1866 |
A A 1869 1872 |
For instance, Sir J. Lubbock has recently shown that a 1866 |
certain ephemerous insect (Chlöeon) during its
development, development, 1869 1872 | development 1866 |
moults, moults, 1869 1872 | moults 1866 |
as shown by Sir J. Lubbock, above as shown by Sir J. Lubbock, above 1869 1872 |
above 1866 |
twenty times, and each time undergoes a certain amount of change;
and in this and in this 1869 1872 |
in such 1866 |
case
we
see see 1869 1872 | probably behold 1866 |
the act of metamorphosis
performed in a primary and gradual manner. performed in a primary and gradual manner. 1869 1872 |
in its natural or primary progress. 1866 |
↑4 blocks not present in 1859 1860 1861 1866 1869; present in 1872 | Many insects, and especially certain crustaceans, show us what wonderful changes of structure can be effected during development.
Such changes, however, reach their climax in the so-called alternate generations of some of the lower animals.
It is, for instance, an astonishing fact that a delicate branching coralline, studded with polypi and attached to a submarine rock, should produce, first by budding and then by transverse division, a host of huge floating jelly-fishes; and that these should produce eggs, from which are hatched swimming animalcules, which attach themselves to rocks and become developed into branching corallines; and so on in an endless cycle.
The belief in the essential identity of the process of alternate generation and of ordinary metamorphosis has been greatly strengthened by Wagner's discovery of the larva or maggot of a fly, namely the Cecidomyia, producing asexually other larvæ, and these others, which finally are developed into mature males and females, propagating their kind in the ordinary manner by eggs.
|
Many insects, and especially certain crustaceans, show us what wonderful Many insects, and especially certain crustaceans, show us what wonderful 1869 |
What great 1866 |
changes of structure
can be
effected during
..
development. development. 1869 | development 1866 |
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
....... 1869 | crustaceans. 1866 |
Such changes, however, reach their climax in Such changes, however, reach their climax in 1869 |
When, however, we read of the several wonderful cases, recently discovered, of 1866 |
the so-called alternate generations of
some of the lower animals. some of the lower animals. 1869 |
animals, we come to the climax of developmental transformation. 1866 |
It is, for instance, an astonishing fact It is, for instance, an astonishing fact 1869 |
What fact can be more astonishing than 1866 |
that a delicate branching coralline, studded with polypi and attached to a submarine rock, should produce, first by budding and then by transverse division, a host of huge floating jelly-fishes; and that these should produce eggs, from which are hatched swimming animalcules, which attach themselves to rocks and become developed into branching corallines; and so on in an endless
cycle.
↑1 blocks not present in 1859 1860 1861 1869 1872; present in 1866 | Hence it will be seen that I follow those naturalists who look at all cases of alternate generation, as essentially modifications of the process of budding, which may supervene at any stage of development.
|
The belief in the essential identity The belief in the essential identity 1869 |
This view 1866 |
of the
process of process of 1869 |
close connection between 1866 |
alternate
generation generation 1869 | generations 1866 |
and
of ordinary of ordinary 1869 | ordinary 1866 |
metamorphosis metamorphosis 1869 | metamorphoses 1866 |
has
..
been
greatly
strengthened by
Wagners Wagners 1869 | Wagner's 1866 |
discovery of the larva
or or 1869 |
of a Cecidomyia,— that is of the 1866 |
maggot of a
fly, namely the Cecidomyia, fly, namely the Cecidomyia, 1869 |
fly,— 1866 |
producing asexually
...OMIT 1869 |
within its body 1866 |
other and similar
larvæ.
..
..
..
..
..
↑Subtitle not present 1866 1869 1872 |
Embryology
.— 1859 1860 1861 |
|
It has already been
stated that various parts and organs stated that various parts and organs 1869 |
casually remarked that certain organs 1859 1860 1861 |
remarked that various parts and organs of the same individual animal are during an early embryonic period exactly like each other, but become 1866 |
stated that various parts 1872 |
in the
same individual are exactly like each other during an early embryonic period, but in the adult state become widely different and serve for widely different purposes. same individual are exactly like each other during an early embryonic period, but in the adult state become widely different and serve for widely different purposes. 1869 |
individual, which when mature become widely different and serve for different purposes, are in the embryo exactly alike. 1859 1860 1861 |
adult state widely different and serve for widely different purposes. 1866 |
same individual which are exactly alike during an early embryonic period, become widely different and serve for widely different purposes in the adult state. 1872 |
So again it has
....... 1869 1872 | already 1866 |
been
stated stated 1869 | remarked 1866 | shown 1872 |
that
the the 1866 1869 | generally the 1872 |
embryos of
the most distinct species within the most distinct species within 1869 |
distinct species and genera within 1866 |
the most distinct species belonging to 1872 |
the same class are
generally generally 1866 1869 | generally 1872 |
closely similar, but
become become 1866 1869 | become, 1872 |
when fully
developed developed 1866 1869 | developed, 1872 |
widely dissimilar. A better proof of this latter fact cannot be given than
that that 1866 1869 | the statement 1872 |
by Von
Baer,
|