Cyclostomes

He points out first that Cyclostomes are degenerate fish, half specialised and half degraded in adaptation to a parasitic mode of life.

Form and Function A Contribution to the History of Animal Morphology

He recognises as the basis of his comparisons the homology of the notochord in all vertebrate embryos with the persistent notochord which forms the chief part or the whole of the vertebral column in the Cyclostomes.

Form and Function A Contribution to the History of Animal Morphology

It resembles on its first appearance, in form, position, composition, and connections, the ear-capsule of Cyclostomes, and so do the ear-capsules of all embryonic Vertebrates (p. 39).

Form and Function A Contribution to the History of Animal Morphology

Cyclostomes were in the same way the degenerate modern representatives of the ancestral Protovertebrates.

Form and Function A Contribution to the History of Animal Morphology

Teleosteans, and also found no hypertrophy of the follicle in Cyclostomes which are also oviparous.

Hormones and Heredity J. T. Cunningham 1897

The notochord is the supporting axis of the pioneer backboned animals, namely the Lancelets and the Round-mouths (Cyclostomes), such as the

The Outline of Science, Vol. 1 (of 4) A Plain Story Simply Told J. Arthur Thomson 1897

All the Gnathostomes have these three canals like man, whereas among the Cyclostomes the lampreys have only two and the hag-fishes only one.

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

This first structure of the human heart, enclosing a very simple cavity, corresponds to the tunicate-heart, and is a reproduction of that of the Prochordonia, but it now divides into two, and subsequently into three, compartments; this reminds us for a time of the heart of the Cyclostomes and fishes.

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

But as the olfactory nerve is double in both cases, it is possible that the peculiar form of the nose in the actual Cyclostomes is a secondary acquisition (by adaptation to suctorial habits).

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

Cyclostomes are still very limited, though they have a brain.

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