The Crayfish: An Introduction to the Study of Zoology.

Name: The Crayfish: An Introduction to the Study of Zoology.
Author: Huxley, Thomas Henry

Huxley, Thomas Henry

Crayfish; Zoology

I. Recent.                     _Potamobiidæ._     _Homarina._       _Penæus._
 ────────────────────────────────────|─────────────────|────────────────────|──
 II. Later Tertiary.  _Astacus_      |                 |                    |
                     (Idaho).        |                 |                    |
 ────────────────────────|───────────|─────────────────|────────────────────|──
 III. Earlier Tertiary.  |           |             _Hoploparia._            |
 ────────────────────────|───────────|──────────────────────────────────────|──
 IV. Cretaceous.  _Astacus._ _Pseudastacus._ _Enoploclytia._ _Hoploparia._  |
 ────────────────────────────\─────────────────────────────/────────────────|──
 V. Wealden                   \                           /                 |
     (Fresh Water).            \                         /                  |
 ───────────────────────────────\───────────────────────/───────────────────|──
 VI. Jurassic.              _Pseudastacus._         _Eryma._          _Penæus._
 ─────────────────────────────────|────────────────────|────────────────────|──
 VII. Liassic.                    |                 _Eryma._          _Penæus._
 ──────────────────────────────────────────────────────────────────────────────
 VIII. Triassic.
 ──────────────────────────────────────────────────────────────────────────────
 IX. Permian.
 ──────────────────────────────────────────────────────────────────────────────
 X. Carboniferous.                 _Anthrapalæmon._
 ──────────────────────────────────────────────────────────────────────────────
 XI. Devonian.
 ──────────────────────────────────────────────────────────────────────────────
 XII. Silurian.
 ──────────────────────────────────────────────────────────────────────────────
 XIII. Cambrian.

If an Astacomorphous crustacean, having characters intermediate
between those of _Eryma_ and those of _Pseudastacus_, existed
in the Triassic epoch or earlier; if it gradually diverged into
Pseudastacine and Erymoid forms; if these again took on Astacine
and Homarine {346} characters, and finally ended in the existing
_Potamobiidæ_ and _Homarina_, the fossil forms left in the track of
this process of evolution would be very much what they actually are.
Up to the end of the Mesozoic epoch the only known _Potamobiidæ_
are marine animals. And we have already seen that the facts of
distribution suggest the hypothesis that they must have been so, at
least up to this time.

Thus, with respect to the Ætiology of the crayfishes, all the known
facts are in harmony with the requirements of the hypothesis that
they have been gradually evolved in the course of the Mesozoic
and subsequent epochs of the world’s history from a primitive
Astacomorphous form.

Public-domain text, read in full here on John Shaqi.

Opening the text

The Crayfish: An Introduction to the Study of Zoology.Huxley, Thomas Henry

Science

The Crayfish: An Introduction to the Study of Zoology.

Huxley, Thomas Henry

Crayfish; Zoology

I. Recent.                     _Potamobiidæ._     _Homarina._       _Penæus._
 ────────────────────────────────────|─────────────────|────────────────────|──
 II. Later Tertiary.  _Astacus_      |                 |                    |
                     (Idaho).        |                 |                    |
 ────────────────────────|───────────|─────────────────|────────────────────|──
 III. Earlier Tertiary.  |           |             _Hoploparia._            |
 ────────────────────────|───────────|──────────────────────────────────────|──
 IV. Cretaceous.  _Astacus._ _Pseudastacus._ _Enoploclytia._ _Hoploparia._  |
 ────────────────────────────\─────────────────────────────/────────────────|──
 V. Wealden                   \                           /                 |
     (Fresh Water).            \                         /                  |
 ───────────────────────────────\───────────────────────/───────────────────|──
 VI. Jurassic.              _Pseudastacus._         _Eryma._          _Penæus._
 ─────────────────────────────────|────────────────────|────────────────────|──
 VII. Liassic.                    |                 _Eryma._          _Penæus._
 ──────────────────────────────────────────────────────────────────────────────
 VIII. Triassic.
 ──────────────────────────────────────────────────────────────────────────────
 IX. Permian.
 ──────────────────────────────────────────────────────────────────────────────
 X. Carboniferous.                 _Anthrapalæmon._
 ──────────────────────────────────────────────────────────────────────────────
 XI. Devonian.
 ──────────────────────────────────────────────────────────────────────────────
 XII. Silurian.
 ──────────────────────────────────────────────────────────────────────────────
 XIII. Cambrian.

If an Astacomorphous crustacean, having characters intermediate
between those of _Eryma_ and those of _Pseudastacus_, existed
in the Triassic epoch or earlier; if it gradually diverged into
Pseudastacine and Erymoid forms; if these again took on Astacine
and Homarine {346} characters, and finally ended in the existing
_Potamobiidæ_ and _Homarina_, the fossil forms left in the track of
this process of evolution would be very much what they actually are.
Up to the end of the Mesozoic epoch the only known _Potamobiidæ_
are marine animals. And we have already seen that the facts of
distribution suggest the hypothesis that they must have been so, at
least up to this time.

Thus, with respect to the Ætiology of the crayfishes, all the known
facts are in harmony with the requirements of the hypothesis that
they have been gradually evolved in the course of the Mesozoic
and subsequent epochs of the world’s history from a primitive
Astacomorphous form.

Public-domain text, read in full here on John Shaqi.

The Crayfish: An Introduction to the Study of Zoology.

The Crayfish: An Introduction to the Study of Zoology.

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