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1859
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1859
1860
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correlated with others, 1859 1860 1861 1866 1869
in combination, 1872

1 blocks not present in 1859 1860 1861; present in 1866 1869 1872
Thus, as Fritz Müller has lately remarked, in the same group of crustaceans, Cypridina is furnished with a heart, whilst in two closely allied genera, namely Cypris and Cytherea, there is no such organ; one species of Cypridina has well-developed branchiæ, whilst another species is destitute of them.

any in the classification of animals; 1859 1860 1861 1866
all; 1869 1872

true. 1859 1860 1861 1869 1872
true, though its importance has sometimes been exaggerated. 1866

The same fact holds good with flowering plants, of which the two main divisions have been founded on characters derived from the embryo,— on the number and position of the em- bryonic leaves or cotyledons, and on the mode of development of the plumule and radicle. 1859 1860 1861
The general fact of the importance of embryological characters holds good with flowering plants, of which the two main divisions have been founded on differences in the embryo,— on the number and position of the cotyledons, and on the mode of development of the plumule and radicle. 1866
Nevertheless their importance has sometimes been exaggerated; in order to show this, Fritz Müller arranged by the aid of such characters the great class of crustaceans, and the arrangement did not prove a natural one. 1869

not trouble themselves about the physiological value of the characters which they use in defining a
group
group,
or in allocating any particular species. If they find a character nearly uniform, and common to a great number of forms, and not common to others, they use it as one of high value; if common to some lesser number, they use it as of subordinate value. This principle has been broadly confessed by some naturalists to be the true one; and by none more clearly than by that excellent botanist, Aug. St. Hilaire. If
several trifling
certain
characters are always found correlated with others, though no apparent bond of
connection
connexion
can be discovered between them, especial value is set on them. As in most groups of animals, important organs, such as those for propelling the blood, or for
aërating
aerating
aërating
it, or those for propagating the race, are found nearly uniform, they are considered as highly serviceable in classification; but in some groups
of animals
of animals
all these, the most important vital organs, are found to offer characters of quite subordinate value.
We can see why characters derived from the embryo should be of equal importance with those derived from the adult, for
a natural
our
classification
classifications
of course
includes
include
all
ages.
ages
of
of
each
each
species.
species.
But it is by no means obvious, on the ordinary view, why the structure of the embryo should be more important for this purpose than that of the adult, which alone plays its full part in the economy of nature. Yet it has been strongly urged by those great naturalists, Milne Edwards and Agassiz, that
embryological
embryonic
characters are the most important of any in the classification of animals; and this doctrine has very generally been admitted as true. The same fact holds good with flowering plants, of which the two main divisions have been founded on characters derived from the embryo,— on the number and position of the em- bryonic leaves or cotyledons, and on the mode of development of the plumule and radicle.