President's Address. 189 
the technical terms used in zoological descriptions throughout 
the whole range of the animal kingdom, terms which are often 
very difficult from books alone to learn rightly to understand 
and apply. Here also may be placed illustrations of general 
phenomena, such as mimicry, adaptation to surroundings, 
etc., as in the telling examples already placed in the Index 
Collection at the British Museum. 
Then, to illustrate the leading principles of classification, 
it should also contain a limited but carefully selected series 
of specimens of animals from all the great divisions, down at 
least as far as the groups conventionally termed orders; while 
there should be intermixed with them a sufficient number 
of skeletons, dissections, and anatomical and embryological 
models, to show in what manner modern ideas of classification 
are founded upon structure and development. Throughout 
the collection, things which are microscopic should also be 
represented by enlarged models or drawings. 
Here also paleontology should not be neglected; but 
extinct orders, such as Trilobita, Eurypterina, Ichthyosauria, 
Plesiosauria should be represented, in their proper places in 
the zoological system along with the recent ones, by good, 
clear specimens, if such are procurable, or by good casts, if 
originals cannot be obtained. The labels attached to the 
specimens in the type collection should be abundantly 
descriptive and explanatory—not exactly taking the place 
of a text-book, however, for though zoology cannot be learned 
without specimens, neither can books be dispensed with. 
But, indeed, a well-written descriptive catalogue of such a 
collection, when completed, would form a text-book of very 
considerable value to all classes of students. 
Then, though I cannot see the necessity for arranging the 
cases in the form of a genealogical tree, I would have no 
objection to indicate the latest views on the phylogeny of 
the various groups by means of diagrams, always, however, 
taking care to make the student bear in mind that such 
views, however probable they may be in many cases, are yet 
after all in most only hypothetical. 
You will say that this is just the sort of collection which, 
under the name of Index Collection, is now being put up in 
VOL. XI. 0 
