92 SECRETS OF ANIMAL LIFE 



tive chain, the pound of flesh will be, so to speak, 

 cheaper. Thus a pound of plaice is said to require 

 to begin with only 100 Ib. of vegetable material. 

 But the basal fact is clear that just as all flesh is 

 "grass," so sooner or later all fish is " seaweed." 



In spite of the old saying, Vitior alga, " More 

 worthless than seaweed," these humble plants have 

 many uses, e.g. in making mannite, mucilage, and 

 manure. The nutritive value of seaweed is, indeed, 

 an old story; the streets of Edinburgh used to 

 resound with the shrill cry of the fishwives 

 "Wha'll buy dulse and tangle?" but what science 

 has shown is that the indirect importance is much 

 greater than the direct. 



It is plain, then, that fishes are far from being 1 

 economical to produce. They are like a super- 

 structure that requires a very broad and costly 

 foundation. The quantity of humbler life that 

 makes the food-fishes almost wholly carnivorous 

 possible is enormous; and the estimate has to be 

 increased when we remember that a great proportion 

 of the weight of an animal which a fish devours 

 may be quite useless e.g. the water in its tissues 

 and the shell of lime. Thus we are naturally led to 

 Professor Petersen's important practical conclusion 

 that the quantity of fishes which an area of sea 

 can support is anything but unlimited. In some 

 restricted bays, indeed, he found strong reasons for 

 suspecting that the limit had been reached. That 

 this limit is a generous one is an important fact for 

 man, for the Danish fishermen took about 60,000 



