to pick out the insects as one group and to call everything else “Vermes” or worms.  The insects included all creatures possessed of an external skeleton or hard skin divided into jointed segments, and included forms so different as insects, spiders, crabs, and lobsters.  But Vermes included all the members of the animal kingdom that were neither vertebrates nor insects.  Cuvier advanced a little.  He got rid of the comprehensive title Vermes—­the label of the rubbish-heap of zooelogists.  He divided animals into four great subkingdoms:  Vertebrates, Mollusca, Articulata, Radiata.  These names, however, only covered very superficial resemblances among the animals designated by them.  The word Mollusca only meant that the creatures grouped together had soft bodies, unsupported by internal or external articulated skeletons; and this character, or, rather, absence of character, was applied alike to many totally dissimilar creatures.  The term Articulata included not only Linnaeus’s insects but a number of soft-skinned, apparently jointed, worm-like animals such as the leech and earthworm.  Lastly, the name Radiata meant no more than that the organs of the creatures so designated were more or less disposed around a centre, as the sepals and petals of a flower are grouped around the central pistil; and it included animals so different as the starfish and sea-anemones and Medusae.  The names used in the classification were not only loosely applied but were based on the most superficial observation, and took no account of the intimate structures of the tissues and organs of the animals.  With slight modifications, due to individual taste or special knowledge of small groups, later writers had followed Linnaeus and Cuvier.

It was with a view of the animal kingdom not much clearer than this that Huxley began his work on the Medusae of the tropic seas.  He began to study them no doubt simply because they were among the most abundant of the animals that could be obtained from the ship.  He made endless dissections and drawings, and, above all, studied their minute anatomy with the microscope.  They were all placed among Cuvier’s Radiata, but, as Huxley said in the first line of his memoir: 

“Perhaps no class of animals has been investigated with so little satisfactory and comprehensive result, and this not for the want of patience and ability on the part of the observers, but rather because they have contented themselves with stating matters of detail concerning particular genera and species, instead of giving broad and general views of the whole class, considered as organised upon a given type, and inquiring into its relations with other families.”

He found that fully developed Medusae consisted each of a disc with tentacles and vesicular bodies at the margins, a stomach, and canals proceeding from it, and generative organs.  He traced this simple common structure through the complications and modifications