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NATURE 
203 

27 feet in breadth, the total length being 250 feet. Space 
was thus provided for eighteen table-cases, each ro feet 
long, set transversely. One important point was there- 
fore settled by the shape of the building. The series had 
to be conformed to a linear arrangement. In some 
respects this was a serious disadvantage. The classes of 
Invertebrate animals cannot well be represented in a 
single ascending or descending series. Probably it would 
not be possible on any symmetrical plan to indicate their 
proper positions relatively to each other; but some 
palpable incongruities might be avoided by the use of 
table-cases ona ground-plan, resembling in form a tuning- 
fork. The Protozoa, as the stem, pass naturally enough on 
one side by the Rotiferze and their allies to the Annelida, 
Echinodermata, Crustacea, and Insecta ; and on the other 
by the Coelenterata to the Molluscoida and Mollusca ; the 
greater size of the specimens forming the latter prong of 
the fork, compensating for the vastly more numerous 
species in the former. The importance of a suitable 
ground-plan for cases in Museums seems to be much 
underrated. When a class” of students visit a museum 
frequently, the localities of cases containing special groups 
become indelibly impressed upon the memory. Why 
should not this be turned to good account? 
In preparing the first scheme of the collection, it seemed 
to me essential that plain, and moderately simple, printed 
descriptions of the life history of the animals should ac- 
company the specimens, but, as it was clearly impossible 
to describe every species, or even every genus, it became 
necessary to fix on some mode of associating in groups a 
number of species to which the descriptions might apply. 
Such divisions as “classes ” and “ orders ” were manifestly 
too large ; whilst “families” varied from a single genus, 
including a solitary species, to an army of more than a 
thousand genera, ¢.g. the Cerambycidz and Curculionidze 
in the Coleoptera. It was with some regret that the idea 
of attaching a readable sketch to each division of a given 
rank in recent systems of classification was relinquished, 
but it was found to be impracticable ; and the life history 
sketch thus became the foundation of the system even- 
tually adopted. Whether it might be a few species, or a 
genus, or a family, or an order, that seemed to afford 
suitable scope for a paragraph of readable and instructive 
matter, it was decided that such a group should be segre- 
gated, so as to form the unit of the series. Eventually, 
in order that the sketches, which it was proposed to print 
for the purpose on tablets, might all be in positions where 
they could conveniently be read, it was found to be ex- 
pedient that each group, or unit, should occupy an equal 
“space ; and as the blocks on which the table-cases rested 
were to be fitted up with trays or drawers, twelve of which 
would occupy the table-case without loss of room, these 
trays or drawers were adapted as the receptacles and 
boundaries of the groups. 
The drawers measured twenty-seven inches in length by 
sixteen inchesin breadth, and their number in the eighteen 
table-cases, when completed, would be 216. Then arose 
the problem, how best to divide the twenty classes of 
Invertebrate animals into 216 groups, each of which should 
be capable of affording materials for a biological notice, 
such as might be read with interest by any intelligent 
visitor. ; 
The entire plan of the table-cases, and the limits of 

most of the groups, were committed to writing before any 
considerable advance had heen made in procuring speci- 
mens. In one respect this circumstance was found to be 
very advantageous—our deséderata were at once well- 
defined. It was an object that each of the groups should 
be illustrated by carefully selected specimens, and until 
this could be attained, other acquisitions need not be 
sought for. In making purchases, such an object steadily 
kept in view exercises a powerful influence against the 
seductive attractions of “great bargains,” which often 
turn out to be great misfortunes to a Museum. More- 
over, in accepting donations, it issometimes convenient to 
be able to refer toa fixed plan. Where room is scanty, 
as in most Museums, nothing is more subversive of order, 
or more fatal to an instructive arrangement, than the gift 
of a collection, coupled with a stipulation that it must be 
displayed in some special way. It is far better to forego 
the possession even of a valuable series of specimens, 
than to sacrifice order for their sake. 
The number of groups, 216, will, no doubt, appear to 
have been determined simply as a matter of convenience. 
To a certain extent this is true. After a careful reference 
to the best available authorities on each of the Inverte- 
brate classes, in which much assistance was afforded me 
by the many valuable scientific works in the Free Public 
Library of Liverpool, and by the catalogues of the collec- 
tions in the British Museum, it seemed probable that most 
of the prominent forms in all the classes might be ex- 
hibited in pairs, with their names attached in very legible 
type, in an area less than a thousand square feet ; and 
that they might appropriately be disposed in 240 groups, 
occupying twenty table-cases. For these, the suite of five 
rooms above referred to would have been sufficient, but 
two large circular stoves occupied the room of two table- 
cases, and the groups had to be reduced to 216 in num- 
ber, instead of 240, as in the original design. 
For constant exhibition to the public, the series may 
perhaps be regarded as quite sufficiently extensive. Four 
table-cases contain the Protozoa and the Ccelenterata, 
Seven are given to the Molluscoida and Mollusca, in 
which department the collection includes representatives 
of about eleven hundred out of the thirteen hundred genera 
and sub-genera adopted by Messrs. H. and A. Adams in 
their work on “ The Genera of recent Mollusca.” Three 
cases are occupied by Echinodermata, Annelida, and Crus- 
tacea. This is by no means in proportion to the other 
parts of the series, and here it is that the want of the two 
absent table-cases is most felt. Four cases hold the Arach- 
nida, Myriapoda, and Insecta, in which all the orders are 
fairly illustrated, except Strepsiptera. Stylops has not yet 
arrived—perhaps this may meet the eye of some friend 
who, for love, money, or specimens, may be willing to 
supply the deficiency. 
It is hardly necessary for me to point out the difficulties 
and disadvantages which must attend an attezipt to form 
a collection in which the whole of the Inverteb_ ate classes 
are divided into a given number of equal groups. If all 
very distinct forms are to be exhibited, some groups must 
be heterogeneous in composition, but not necessarily very 
many. Such forms as Pycnogonum, Forficula, Siphon- 
aria, Sagitta, Cydippe, &c., may have to appear as inter- 
lopers ; but the printed tablet may explain the irregularity 
of their position, and render the disadvantage simply a 
