The shell-fish with which he dealt specially were those distinguished as Cephalous, because, unlike creatures such as the oyster and mussel, they had something readily comparable with the head of vertebrates.
"Thomas Henry Huxley; A Sketch Of His Life And Work"
P. Chalmers Mitchell
The anatomy of many of the Cephalous molluscs was known, but the relation of structures present in one to structures present in another group had not been settled.
"Thomas Henry Huxley; A Sketch Of His Life And Work"
P. Chalmers Mitchell
He shewed how the widely different groups of Cephalous molluscs could be conceived as modifications of this structure, and extended the conception so as to cover all other molluscs.
"Thomas Henry Huxley; A Sketch Of His Life And Work"
P. Chalmers Mitchell