214 Fortieth Animal Meeting 



engers — snails, hermit-crabs, shrimps, and prawns. The 

 entire econom)^ of the waters is filled and delicately bal- 

 anced, not a link is wanting. 



The nekton, too, is present, including most of our impor- 

 tant food fishes, for the rich pasturage of the shore attracts 

 them in its season, and part feast on it gluttonously, while 

 others feast on the feasters. Some are there for depositing 

 their eggs, that their young may hatch in the midst of 

 plenty, others, instinctively fearing the multitude, search 

 for secluded places. Some, like the salmon and sturgeon, 

 ascend the rivers to their very sources to give the coming 

 generation a chance to develop as far as possible from the 

 liungry horde. Everywhere the devourers intensify the 

 struggle for existence, and yet at the same time each 

 searches out the locality best suited for its specific peculiari- 

 ties, and when that is found the struggle renews with those 

 of its own kind or with others of similar needs. Thus the 

 already specialized littoral fauna becomes more and more 

 interlocked with its environment, until some disturbing or 

 eliminating factor, some sudden change of temperature, 

 perhaps, causes the temporary disappearance of a link and 

 the balance is upset, only to be reestablished along other 

 lines. And here again the food relation brings us back to 

 the plankton as the ultimate source of nutrition. An excel- 

 lent illustration of its inevitability is quoted herewith from 

 Peck's researches on the squeteague : "On the morning of 

 July 23d there was taken a large specimen (of squeteague) 

 whose stomach contained an adult herring, in the stomach 

 of the herring were found two young scup (besides many 

 small Crustacea), and in the stomach in one of these young 

 scup were found copepods, while in the alimentary tract of 

 these last one could identify one or two of the diatoms and 

 an infusorian test among the mass of triturated material 

 which formed its food. * * * And the food of the sque- 

 teague must be regarded as a complex of all these factors, a 

 resultant of several life histories to a given environment." 

 A contrasted instance to this is that of the menhaden, that 

 great food-fish for food-fishes, which itself feeds directly 

 upon nothing but the microorganisms of the plankton. 



