384 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



Besides the diatoms some lower algae 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 higlier algai growing 

 on oyster beds will prove to be an additional source of oyster food. I 

 therefore nnule a list of the alga^ 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 alga\ For this reason the small 

 number of species collected is not to be wondered at.* 



Algw collected. 



1. Melanophycefe. 



Fucus vesiculosns. 



Cblorophyce.'p. 



Bryopsis phimosa. 

 Ulva lactuca. 

 Ulva clathrata. 

 Ulva hopkirkii. 

 Cladophora, sp. 

 Entocladia viridis. 



3. Floride.-p. 



Dasya elegans. 

 Chondria teuuissima. 

 Polysiphonia varieji^ata. 

 Ehabdonia tencra. 

 Ceramium rubrum. 

 Gracelaria conipressa. 

 Polysipbonia uiceolata. 



4. Cyauopbyce.TB. 



Lyngitya, sp. 

 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 exam])le, cattle live directly on plants, 



*Tbat tbo flora at Hampton is very rnucb ricbcr is strongly snggested by tbe fact 

 that \\\ April of tliis year, during an afternoon vralk along tbe sborc, I found in great 

 abundance Pliyllitis, Ectocarpus, Pelagella, three genera of which in August no 

 trace was left. 



