vertebrates

Owen says that the thymus appears in vertebrates with the establishment of the lung as the main or exclusive respiratory organ.

The only example among vertebrates is that of the beavers, members of the low order of rodents.

There remain for consideration the lesser mammals and other vertebrates whose fecundatory instruments resemble those of mammifera.

The amphioxus, the bridge between invertebrates and vertebrates, is not hermaphrodite.

Of vertebrates, we may find the bones and teeth of amphibians, reptiles, birds and mammals.