it is not imperative on others to adopt the trivial name imposed, 
or recognise it in any way. The want of short characters (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. In composing 
either a defining character or a detailed description, it is also neces- 
sary to use the technical language of that science. The author, in 
referring to Dr Gregory’s paper on the Diatomaceee of the Clyde, 
published in the last part of the Transactions , regretted that this 
patient observer had neglected these rules, and thus enveloped his 
whole memoir in an almost impenetrable cloud ; thus not only pre- 
cluding himself from claiming any right of priority of names, in the 
event of the same form being afterwards correctly characterized by 
another under a different name, but depriving the paper itself of its 
claims to be considered a scientific one. The same unfortunate 
cloud rendered it difficult to understand what Dr Gregory’s actual 
views of the structure of Amphora were ; although, from expressions 
used by him, he appears to enunciate the theory, that what other 
writers call a simple frustule, ought to be considered as a double 
one. 
The author, to make this more intelligible to those not generally 
interested in such pursuits, defined what the structure of a diatom 
was, as is explained by Smith in his Synopsis of British Diatomacese ; 
and indicated the mode of proving, by Canada balsam, whether the 
frustule was single or double. When tested in this way, what was 
commonly called a simple frustule was found to be actually so, and 
of one cell, so that Dr Gregory’s hypothesis was untenable. The 
structure of the genus Amphora appears to have been also slightly 
misunderstood by Kutzing and Smith. The real form of the frus» 
tule is not a spheroid, as they must have considered it, but rather 
like that of a coffee-bean, rounded at the back and hollowed out in 
front, the line connecting the two terminal and central nodules of 
each valve being the median line ; this line and the central nodule 
are thus not marginal, as hitherto described, but exactly as in 
other diatoms in which such are found. An Amphora would thus 
chiefly differ, by the half of the valve on the one side of the median 
line being concave, while the other was convex ; whereas, in most 
