| → OMIT 1869 1872 |
| as it certainly is, 1859 1860 1861 1866 |
|
| → to be true 1869 |
| to be the case 1859 1860 1861 1866 |
| OMIT 1872 |
|
| → legs, a very 1859 1860 1861 1866 1869 |
| locomotive organs, a 1872 |
|
|
cases, however, the
though active, still
more or less
the law of common embryonic resemblance. Cirripedes afford a good instance of
even the illustrious Cuvier did not perceive that a barnacle
→OMIT
a crustacean; but a glance at the larva shows this
→to be true
in an
manner. So again the two main divisions of cirripedes, the pedunculated and sessile,
widely in external appearance, have larvæ in all their
stages barely distinguishable. |
|
| The embryo in the course of development generally rises in
I use this expression, though I am aware that it is hardly possible to define clearly what is meant by the organisation being higher or lower. But no one probably will dispute that the butterfly is higher than the caterpillar. In some cases, however, the mature animal
considered as lower in the scale than the larva, as with certain parasitic crustaceans. To refer once again to cirripedes: the larvæ in the first stage have three pairs of
→legs, a very
simple single eye, and a probosciformed mouth, with which they feed largely, for they increase much in size. In the second stage, answering to the chrysalis stage of butterflies, they have six pairs of beautifully constructed natatory legs, a pair of magnificent compound eyes, and extremely complex
but they have a closed and imperfect
and cannot feed: their function at this stage is, to search
their well-developed organs of sense, and to reach by their active powers of swimming, a proper place on which to become attached and to undergo their final metamorphosis. When this is completed they are fixed for life: their legs are now converted into prehensile organs; they again obtain a well-constructed mouth; but they have no antennæ, and their two eyes are now reconverted into a minute, single,
|
