SEA-MEADOWS 91 
animals shows that the food consumed consists very 
largely of this valuable débris, Thus the main 
food of oysters and other bivalves is vegetable dust 
“which is found, either in suspension in the water, 
or deposited as the thin upper layer of the bottom 
itself, lifting and spreading at times in stormy 
weather, but only to be precipitated anew later on.” 
Some of Professor Petersen’s statistics are very 
interesting. His valuation of the sea-meadows of 
Danish waters inside the Skaw shows a total of 
24 million tons for the plants, 5 million tons for 
those animals that are “useless” both directly and 
indirectly, 1 million tons for the “useful” forms 
that furnish or may furnish food for fishes, and only 
some few thousands of tons (5 to 7000) for each of 
the short list of valuable food fishes, such as plaice 
and cod. Starfishes make up 25,000 tons, more 
than all the important food fishés lumped together, 
while crabs and Gastropods amount to no less than 
50,000 tons. We see that food-fishes form only 
an insignificant part of the total stock of animal 
life in waters like the Kattegat. The reason is to 
be found in the relations that govern the circulation 
of matter or the metabolism of the sea. To make a 
pound of cod requires 10 lb. of whelk or buckie; 
to make a pound of buckie requires to lb. of 
worms; to make a pound of worm requires Io Ib. 
of vegetable matter, which may be given in the 
form of dust! So a pound of a carnivorous fish 
like a cod requires 1000 lb. of sea-grass. If there 
be fewer links in the House-that-Jack-built nutri- 
