Origin of Species Variorum

→ yet nearly all pass through a similar worm-like stage of development; 1859 1860 1861 1866

or from being fed by their parents; 1869 1872

→ by Professor Huxley of the development of this insect, 1859 1860 1861 1866

of the development of this insect, by Professor Huxley, 1869 1872

→ In some cases 1866

Sometimes 1869 1872

→ through the 1866

then through the 1869 1872

→ crustaceans would have appeared as nauplii, if there 1866 1869

OMIT 1872

→ development;— or that they were primordially developed under this form. 1866

development. 1869

development, all these crustaceans would have appeared as nauplii. 1872

→ of embryos of different species within the same class, generally, 1859 1860 1861 1866

the general, 1869

the common, 1872

→ each other;— 1859 1860 1861 1866

between the embryos or larvæ 1869 1872

→ structure of 1859 1860 1861 1866

most distinct species in the same class;— 1869 1872

→ not being closely related to its conditions of existence, existence, except when the embryo becomes at any period of life active and has 1866

not being closely related to its conditions of existence, except when the embryo becomes at any period of life active and has 1859 1860 1861

retaining whilst within the egg or womb, structures which are of no service to it, either at that period or later in life; whilst embryos at a later period, or larvæ, which have 1869

often retaining whilst within the egg or womb, structures which are of no service to it, either at that or at a later period of life; on the other hand larvæ, which have 1872

→ itself;— of the embryo apparently having sometimes a higher 1859 1860 1861 1866

their own wants, are perfectly adapted to the surrounding conditions;— and lastly the fact of certain larvæ standing higher in the scale of 1869

their own wants, being perfectly adapted to the surrounding conditions;— and lastly the fact of certain larvæ standing higher in the scale of 1872

→yet nearly all pass through a similar worm-like stage of development; but in some few cases, as in that of Aphis, if we look to the admirable drawings →by Professor Huxley of the development of this insect, we see

hardly any

trace of the vermiform stage.

→In some cases it is only the earlier developmental stages which

fail.

~~these~~

~~apparently~~

~~having~~

~~been~~

~~suppressed.~~

Thus Fritz

Müller

has

~~recently~~

recently

made the remarkable discovery that certain shrimp-like crustaceans (allied to Penœus) first appear under the simple nauplius-form, and

after passing

passing

through two or more zoea-stages, and →through the mysis-stage, finally acquire their mature structure: now in the whole

great

enormous

malacostracan

order,

class,

to which these crustaceans belong, no other member is as yet known to be first developed under the nauplius-form, though

~~very~~

very

many appear as zoeas; nevertheless

Müller

assigns reasons for his

belief,

belief

that

all

there

these

→crustaceans would have appeared as nauplii, if there had been no suppression of →development;— or that they were primordially developed under this form.

How, then, can we explain these several facts in embryology,—

namely

namely,

the very general,

though

but

not

universal

universal,

difference in structure between the embryo and the adult;—

the various

parts in the same

indivividual

individual

embryo,

embryo

which ultimately become very unlike and serve for diverse purposes, being at

this

early period of growth alike;— →of embryos of different species within the same class, generally, but not

invariable,

universally,

resemblance

resembling

→each other;— of the →structure of the embryo →not being closely related to its conditions of existence, existence, except when the embryo becomes at any period of life active and has to provide for →itself;— of the embryo apparently having sometimes a higher organisation than the mature

animals

animal

animal,

into which

they are

it is

developed.

developed?

I believe that all these facts can be

explained,

ex- plained,