Acrania

Opposed to the Acrania is the second division of the vertebrates, which comprises all the other members of the stem, from the fishes up to man.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

In the Acrania and Cyclostomes and the earlier fishes we can scarcely distinguish a real stomach; it is represented merely by the short piece from the branchial to the hepatic gut.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

In the alimentary apparatus there are the thymus-gland and the thyroid gland, the seat of goitre and the relic of a ciliated groove that the Tunicates and Acrania still have in the gill-pannier; there is also the vermiform appendix to the caecum.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

In the Cyclostoma -- a stage above the Acrania -- the fore end of the cylindrical medullary tube begins early to expand into a pear-shaped vesicle; this is the first outline of an independent brain.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

The Craniota descend directly from the Acrania, and these from the primitive Chordonia.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

There is no trace of these pairs of limbs in the Acrania and

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

The Amphioxus is the only surviving representative of the older and lower section, the Acrania

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

The lowest and earliest Vertebrates, the Acrania and

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

Acrania (Amphioxus) for the phylogeny of the Vertebrate stem.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876

These important parts are wholly wanting in the two lowest classes of Vertebrates, the Acrania and Cyclostoma.

The Evolution of Man — Volume 2 Ernst Heinrich Philipp August Haeckel 1876