242 
On Triceratium and some New Aiiep Forms, with figures. 
of the same. By Surgeon G. C. Watticu, M. D., Bengal 
Army. (Plates Xi, Si: 
«Tir want of short characters,’ observes Professor Walker- 
Arnott, “ (intended to place clearly before the mind the few 
essential points of difference between supposed new and 
already known forms or species) cannot be supplied by figures 
or diffuse descriptions of the entire object, as these leave quite 
in the dark the precise marks of distinction observed by the 
writer, if such actually existed.” 
Toa certain extent this remark is true. But in the present 
state of our knowledge of that class of microscopic organisms 
to which Professor Walker-Arnott refers, its application 1s 
attended with so much difficulty, that, in the absence of 
somewhat detailed description, or accurate figures, the task 
of establishing clear views of special differences of structure 
becomes well nigh hopeless. Theoretically, it may be a 
matter of perfect simplicity to lay down definitions; and 
rules may be offered whereby, in the ordinary researches of 
natural history, such definitions shall be limited to a given 
number of words. But great obstacles present themselves in 
practice, where the microscope stands between the observer 
and the object he is analysing. ‘To describe clearly and con- 
cisely what is seen by the unaided vision, may be an easy 
matter; but, in the case of organisms visible only under a 
high magnifying power, and which demand an experienced 
eye for their interpretation, the case becomes very different. 
It is here that illustrations afford the greatest possible assist- 
ance, and frequently accomplish in a moment what would 
otherwise demand hours of anxious and tedious labour. Good 
definitions are indispensable ; but, under every circumstance, 
their value is much enhanced by well-executed figures. 
We see this exemplified strikingly in the ‘Synopsis of 
British Diatomaceze.’ Nothing can surpass the general con- 
ciseness of the definitions there given; but few will, I pre- 
sume, deny that a number of instances might readily be cited, 
where those definitions would fail to convey the clear com- 
prehension imparted by the masterly figures appended to 
them. 
There is another reason why accurate illustrations are of 
the highest value. As the number of new forms increases, and 
data are thus afforded for revising errors of classification, 
