8 
I. KOBINSOX — THE DIATOMACEiE. 
would indeed appear that notwithstanding their minute size the 
Diatomaceae have added far more to the bulk of the earth’s crust 
than all the gigantic animals of pre-historic times. 
In treating of the classification of the Diatomacese I propose to 
follow the arrangement adopted by Professor Smith in his ‘ Synopsis 
of the British Diatomacese.’ In this work he has described 465 
species found in Great Britain. Of this number 239 are exclusively 
inhabitants of fresh water, 142 are exclusively marine, and the 
remaining 84 may be found in brackish water, but many of them 
are not so decided in their proclivities. He divided the whole of 
this natural order into two tribes. The first of these included all 
those forms the frustules of which are found in a naked condition 
and freely exposed to the surrounding water; and the second, those 
which are enclosed in membranaceous tubes or envelopes. The 
first of these tribes is by far the largest and most important. It 
includes 428 species out of the total of 465, and it is again divided 
into five sub-tribes in accordance with certain characteristics of 
growth. In the first of these sub-tribes the frustules are found 
either in a perfectly free condition, or simply adherent to some 
other substance. It is by far the most numerous of them, embracing 
282 species, and representatives of it are very abundant in our own 
locality. In the second sub-tribe the frustules do not possess the 
power of free motion, but are attached to some other substance, 
either by means of a gelatinous cushion or a dichotomous stipe. 
In the third, the frustules are closely attached to each other, side 
by side, and in this way form filaments of considerable length. 
The filaments are modified in the fourth sub-tribe in consequence 
of the frustules being attached to each other by opposite corners 
only, and thus acquiring a zigzag form. In the fifth and last 
the separate frustules are circular in form, and when closely at¬ 
tached to each other by their surfaces produce cylindrical filaments. 
All these sub-tribes have representatives in our own district. 
In the second tribe the separate frustules are usually enclosed in 
membranaceous tubes, and are often very closely packed in them 
in regular files. The aggregations of these delicate tubes often 
form fronds of considerable size, sometimes an inch or two in 
length, and give them the appearance of very fine Algse. The 
majority of the species included in this tribe are marine, but some 
of thos’e found in fresh water are frequent in this locality. 
In conclusion I would commend the study of the Diatomacese to 
any who have the opportunity of pursuing it, for not only does it 
possess the fascination and charm of a new revelation respecting 
the world around us, but it will I believe enable us to form a very 
much higher mental ideal of the omnipotence of the Creator. In 
the marvellous variety and beauty of design which it affords, in 
combination with an absolute perfection of execution, notwith¬ 
standing an almost inconceivable minuteness in size, we find some 
of the very best possible illustrations of the “ Wondrous works of 
Him which is perfect in knowledge.” 
