SUN AND HARVEST OF THE SEA—SCHMITT 305 
fishes, on the other hand, the food is strained as the water passes 
backward through the mouth between the gill rakers and out of the 
gill openings. The amount of food found in the stomachs of various 
filter feeders examined by investigators is prodigious: a small cope- 
pod was found to contain 120,000 diatoms, a herring, 60,000 copepods, 
a Pacific humpback whale, from 1,500 to 3,000 pounds of sardines, 
besides a miscellaneous lot of smelt, anchovies, hake, shrimp, and 
squids; and a blue or sulphur-bottom whale, which has coarse-fringed 
baleen plates like the humpback, but takes no fish, over 3800 gallons 
of euphausids. For a blue whale to have as much as a ton of crus- 
tacean remains in its stomach is no novelty in some of the larger 
specimens taken in the Antarctic. 
Filter feeders are not the only marine carnivores. Indeed, they 
are the chief sustenance of many other carnivores. The herring is 
an important source of food to many inhabitants of the sea. It is 
preyed upon by innumerable fish (rockfish, cod, haddock, pollock, 
hake, albacore, and dogfish), squid, whales, seals, and porpoises. The 
eges and young of most fish, including the herring, constitute a source 
of food for many predaceous creatures, including the glass or arrow 
worms, the pelagic worm, Zomopteris, and the pelagic amphipod, 
Euthemisto, jellyfish, and comb-jellies. The glass worms, in turn, are 
preyed upon by whales, herring, mackerel, salmon, and medusae. 
The adult herring retaliates for the injury that Tomopteris does to 
its young by making this worm part of its dietary. Huthemisto fur- 
nishes food for more animals than has been hitherto realized. Captain 
Bartlett, who saved the stomachs of many animals that he collected 
in the Arctic regions, found that Huthemisto was eaten in quantity 
by the sulphur-bottom whales, ringed and harp seals, and codfish. 
Mackerel have long been known to relish this amphipod. Though the 
common mackerel is largely a filter feeder, it frequently eats other 
smaller fish—herring, menhaden, anchovies, silversides, and the sand 
lance. The latter at times has been found also in herring stomachs. 
Feeding on the mackerel in turn are sharks, which are said to be their 
worst enemies, cod, bluefish, porpoises, whales, and squid. The larger 
relatives of the mackerel include the tunas and the albacores, both 
voracious carnivores. The salmon at sea are wholly carnivorous. 
Even among the copepods there are some carnivorous species which 
prey on their inoffensive filter-feeding relatives. 
Though some of the more important groups of marine herbivores 
have been briefly discussed, only a few of the many marine carnivores 
have been referred to. It is believed, however, that this discussion 
will give some idea of the food relations of the animals and plants of 
the sea and of the ultimate dependence of the animals, through the 
intermediation of the plants, upon the energy given off by the sun. 
