The idea that there are specific marine counterparts to land creatures,[1] inherited from the writers on natural history in Antiquity, was firmly believed in Islam[2] and in Medieval Europe.
It is exemplified by the creatures represented in the medieval animal encyclopedias called bestiaries, and in the parallels drawn in the moralising attributes attached to each.
The correspondence between the realms of earth and sea, extending to its denizens, offers examples of the taste for allegory engendered by Christian and Islamic methods of exegesis, which also encouraged the doctrine of signatures, a "key" to the meaning and use of herbs.
That there are to be found in the sea the forms, not only of terrestrial animals, but of inanimate objects even, is easily to be understood by all who will take the trouble to examine the grape-fish, the sword-fish, the sawfish, and the cucumber-fish, which last so strongly resembles the real cucumber both in colour and in smell.
"[9] During the Enlightenment the ancient conception was given an innovative and rationalized cast by Benoît de Maillet in describing the transformations and metamorphoses undergone by creatures of the sea to render them fit for life on land, a proto-evolutionist concept, though it was based on superficial morphological similarities: There are in the Sea, Fish of almost all the Figures of Land-Animals, and even of Birds.
[10] Though in Moby-Dick Ishmael, with a nod to Sir Thomas Browne's wording, denies the claim that land animals find their counterparts in the sea:For though some old naturalists have maintained that all creatures of the land are of their kind in the sea; and though taking a broad general view of the thing, this may very well be; yet coming to specialties, where, for example, does the ocean furnish any fish that in disposition answers to the sagacious kindness of the dog?