224 
BULLETIN OF THE NATURAL HISTORY SOCIETY. 
which the sea has access, usually also afford large numbers of 
species. They make up a very considerable proportion of the 
so-called “ plankton ” or assemblage of free swimming micro- 
scope organisms which abound everywhere near the surface of 
the sea, whence they may be obtained by the use of “ plankton 
nets,” constructed of the finest silk gauze, and which are drawn 
through the waters by row boats or motor boats. Many are 
attached to sea-weeds, others to buoys or to the piers of wharves, 
still others, though usually in a dead condition, are found in the 
products of sounding and dredging. Finally, the stomachs of 
fishes and various marine invertebrates often afford a rich 
harvest. 
The Diatoms are of considerable economic interest both 
when living and when dead. It has been stated that they exist 
in countless numbers in all waters, fresh or salt, and hence it is 
not to be wondered at that they play a part of the first 
importance in connection with the food supply of the animal 
life tenanting the same waters. This is directly proved, as just 
stated, by finding them so abundantly in the stomachs of these 
animals ; but it has been further observed, in connection with the 
cultivation of oysters and clams, that these thrive best where 
Diatom life is most abundant, and that the development of 
Diatoms by artificial fertilizers in artificial oyster beds leads to 
a great increase iin the number of the oysters, besides improving 
their quality. Indeed so important is the part taken by Diatoms 
as purveyors of food to marine animals that one writer has 
made the remark that “ All fish are Diatoms,” in the same sense, 
of course, that we also say that “ All flesh is grass.” In other 
words they are, to a great extent, the basis of the food supply 
of the entire animal life of the ocean, even to the highest forms, 
and we cannot attach too much importance to a knowledge of 
everything which concerns their life history and distribution. 
But again, Diatoms are not lost by death. Possessed of 
indestructible silicious skeletons, preserving all their more 
prominent characteristics and still capable of easy identification, 
they simply fall after death to the bottom of rivers, ponds, lakes 
