246 ON NATURAL HISTORY MUSEUMS.
kingdom must needs be superficial and unsound. External characters
always give inadequate notions of structure, whilst in some cases they
even mislead by suggesting false analogies: every one knows that
this is the case, for example, with the group of whales. As compara-
tive anatomy has advanced, the systematic zoologist has been led to
look less at the exterior and more at the interior ; less at the surface
and more at the substance. Supposing we had occasion to classify a
collection of watches, it would clearly be but a poor arrangement to
put all those with gold cases into one group, all with silver cases in
another, with pinchbeck in a third, and so on. We know, in fact,
that the case is but the secondary part of a watch, and that the
essence of its structure is to be found in that assemblage of wheels
which we call the "movement." To understand its structure, there-
fore, we must open each watch; and we can then place together
those which are really similar in essence. We might thus form
several groups, according as the escapement is a verge, or horizontal,
or duplex, or lever. Such an arrangement would certainly commend
itself to the watchmaker, though the dilettante might rest satisfied
with the primitive method of classification by cases. In like manner,
to satisfactorily illustrate and classify a zoological collection, it is
necessary to expose as fully as possible the internal organisation of
the creatures which are represented. Thus, each stuffed specimen
belonging to the great group of backboned animals should be
accompanied by its skeleton; or, failing that, by the skull and other
typical parts. And, if possible, the characters and disposition of the
viscera, or internal organs, should also be exhibited by means of
preserved specimens, by models, and by diagrams. Even where
dissections are introduced, they will afford but little information to
the inexperienced visitor, unless accompanied by corresponding
drawings with clear references to the several organs. Without this, a
stranger standing in front of a preparation usually fails to see anything
but a flabby mass of confused parts dangling in a bottle of spirit ; in
other words, the most careful dissection needs popular interpretation.
Those animals which are destitute of an internal skeleton will of
course be represented by such other hard parts as they may possess ;
but these should stand side by side with preparations, casts, and
diagrams, illustrating their internal economy.
Let it not be supposed that, in advocating as perfect a mode of
illustration as can possibly be attained, I am also advocating the
accumulation of many individual specimens. It seems sufficient,