230 THE SEA FISHERIES 



The results obtained by Brandt, who developed this method, 

 show that the autumn and winter plankton of the Baltic takes a 

 position intermediate between rich pasture and lupiae : — 



Albumen. Fat. Carbohydrates. Ash. 



Rich pasture . 20-6 4-5 64-6 lo-i 



Autumn plankton 20-2-2I-8 2-I-3-2 6o-68-9 8'5-i57 



Lupine . . 20-6 2'6 72-0 4-6 



A group of Infusoria, known as the Peridinians, resemble good 

 grass hay or rye straw : — 



Extracts free 

 Albumen. Fat. from N. Cellulose. Ash. 



Rye Straw . . .3-5 I'S 38-8 51-3 47 



Peridinians . .13-0 1-3 39 41-5 5-2 



Good grass hay . . 13-6 3-2 48-2 26-8 8-2 



On account of their comparatively large amount of albumen, the 

 Peridinians resemble the better kinds of fodder, but their small 

 amount of fat and large amount of cellulose causes them to resemble 

 the poorer sorts. With the approach of spring a remarkable change 

 occurs in the plankton, the percentage of silica becoming much 

 higher, owing to the sudden increase of diatoms. In order to 

 compare diatoms with land plants the weight, free from ash, must 

 be taken : — 



Compared with whole land plants, i.e. excepting special parts, 

 such as rape seed, the percentage of fat in diatoms is invariably 

 found to be much higher, the albumen is also relatively high. On 

 account of the high percentage of fat and albumen and the poverty 

 of carbohydrates, diatoms exhibit a marked contrast to most land 

 plants. It must not be forgotten, however, that more than half 

 the total weight of diatoms consists of silica, which contains no 

 nourishing properties. 



In the summer plankton the animal constituents come into 

 prominence, so that it is no longer possible to compare the analyses 

 with land plants. The albuminous constituents now predominate, 

 fats may be either high or low, carbohydrates are comparatively 

 very low. 



An interesting comparison has been instituted between the 

 Copepoda and certain fish and edible moUusca, The comparison 

 is not so exact as that between the plankton and land plants, 



