78 
GENEEAL ARRANGEMENT. 
upon special circumstances which render the exhibition of the 
leading forms of some groups of more interest than those of 
another. 
While the two series above mentioned have for their 
object the diffusion of scientific knowledge, the next minis- 
ters mainly to its advancement, and thus between them the 
twofold object of a National Museum of Natural History is 
carried out. 
Reserve or HI. The Eeserve or Study Systematic Series contains all 
Systematic those exceedingly numerous specimens (in many groups, the 
Series. great bulk of the collection) showing the minute distinctions 
which are required for working out the problems of variation 
according to age, sex, season and locality, for fixing the limits 
of geographical distribution, or determining the range in geo- 
logical time : distinctions which, in most cases, can only be 
appreciated when the specimens exhibiting them are kept under 
such conditions as to admit of ready and close examination and 
comparison. It is to this part of the collection that zoologists 
and botanists resort to compare and name the animals and plants 
collected in exploring expeditions, to work out biological 
problems, and generally to advance the knowledge of the science. 
In fact, these reserve collections, occupying comparatively little 
room, kept up at comparatively small cost, and visited by com- 
paratively few persons, constitute, from a scientific point of view, 
the most important part of the Museum, for by their means new 
knowledge is obtained, which, given forth to the world in the 
form of memoirs, books, or lectures, is ultimately diffused over 
a far wider area than that influenced even by the exhibited 
portions of the Museum. Indeed, without the means of study 
afforded by the reserve series, the order displayed in arrange- 
ment, the exhibition galleries, and the instruction which can be 
gleaned from the same, would not be possible. 
It is important to bear in mind that if the whole of such 
specimens as are really required for enlarging the boundaries 
of knowledge were displayed in the public galleries, so that 
each one could be distinctly seen, a museum many times larger 
than the present one would not suffice to contain them; the 
specimens themselves would be inaccessible to the exami- 
nation of those capable of deriving instruction from them, and 
