384 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
Besides the diatoms some lower alge were found to be present in the 
water, especially near the shore, and I have no doubt that in winter 
and early spring the reproductive spores of the higher alge growing 
on oyster beds will prove to be an additional source of oyster food. I 
therefore made a list of the alg found during the time of my stay in 
places where oysters were living in the James River. It should be 
borne in mind in connection with this list, however, that my visit was 
made during the hottest months of a very hot summer, a particularly 
unfavorable season for the growth of alge. Tor this reason the small 
number of species collected is not to be wondered at.* 
Alg@ collected. 
1. Melanophycee. 3. Floridex. 
Fucus vesiculosus. Dasya elegans. 
Chondria tenuissima. 
Polysiphonia variegata. 
2. Chlorophycee. Rhabdonia tenera. 
Bryopsis plumosa. Ceramium rubrum. 
Ulva lactuca. Gracelaria compressa. 
Ulva clathrata. Polysiphonia urceolata. 
Ulva hopkirkii. 4. Cyanophycee. 
Cladophora, sp. Lyngbya, sp. 
Entocladia viridis. Oscillaria, sp. 
Looking back on our results, we see that the oyster lives almost 
exclusively on diatoms, and it will be well to recall the structure and 
physiological properties of these low plants. The diatoms are small, 
microscopic plants, surrounded by a firm membrane having a struc- 
ture of a small box; that is, consisting of the two halves of. the cell 
wall, one fitting over the other as the cover does over a pasteboard 
box. These cell walls, formed of cellulose, are incrusted with an 
enormous quantity of silica, often arranged in beautiful and delicate 
designs, so that after the soft parts have been destroyed by heating 
to incandescence, the perfectly clean silicious skeleton remains, show- 
ing all its delicate detail of structure. Inside of this cell wall the 
plasmatic body of the diatom, provided with a nucleus, is seen during 
life. In some species more or less definite portions, in others the whole 
plasma, is diffusely tinged with a brownish color. This color is of par- 
ticular interest to us, for just as the trees, by means of their green 
coloring matter, are able to convert inorganic into organic matter—that 
is, animal food—so are the diatoms in the same way by means of their 
brown color substance. Let us see what this teaches us, and first 
glance at the economic peculiarities of higher animal life. 
Starting from any animal life, we see that its existence always 
depends, either directly or indirectly, on the presence of plants, since 
these alone are able to form organic matter, all animals being destroyers, 
but never producers, of it. For example, cattle live directly on plants, 
*That the flora at Hampton is very much richer is strongly suggested by the fact 
that in April of this year, during an afternoon walk along the shore, I found in great 
abundance Phyllitis, Ectocarpus, Pelagella, three genera of which in August no | 
trace was left. 
