250 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



ably feeds in the same way as tlie generality of the Clupeoids, that is to 

 say, by swimming along with the mouth held o\)en, as I have frequently 

 observed is the habit of the menhaden in its native element. In this 

 way the water which passes through the branchial filter is deprived of 

 the small animals which are too large to pass through its meshes and 

 be swallowed. 



It is a common remark of the fisherman that it is seldom that one 

 finds food in the stomach of the adult shad in freshwater; indeed, 

 from personal observation, it is rare or exceptional. The writer has 

 heard many fishermen express their belief, based on this singular fact, 

 that this fish did not feed at all in fresh water . during the spawning 

 season. With this unreasonable oi)inion I cannot coincide, and I have 

 no doubt but that the shad feeds in fresh water, as well as in the sea, 

 upon such small animals as are liable to be captured by its prehensile 

 apparatus. To show that it does probably capture large numbers of 

 small Crustacea in fresh water, the following observation will show: A 

 spawning female, captured about twenty miles from Washington, down 

 the Potomac, when the stomach was opened, was found to contain about 

 a tablespoonful of Copepoda, apparently a Cyclops, and very similar to 

 the common fresh-water species. This is the only instance in which I 

 found a large amount of food which appeared to have been recently 

 captured, since the carapaces and joints of the antennae and body were 

 still hanging together, with the soft parts partially intact, showing that 

 they had probably been recently swallowed and but partially digested. 

 Upon examining the intestine, however, I invariably found the remains 

 of Copepoda imbedded in the intestinal mucus, the most conspicuous 

 and constant evidence of which was the presence of the hard chitinous 

 jaws (ff these creatures. This was the invariable rule even where there 

 was no food discernible in the stomach. Besides the remains of Cope- 

 poda observed, there were almost invariably present in the intestine 

 green cells, apparently of algous origin; occasionally there were also 

 seen the remains of large crustaceans, possibly shrimps or amphipods, 

 but these were so mutilated and disorganized that the evidence of their 

 presence is founded only upon the occurrence of single joints or frag- 

 ments. The tests of rotifers and the shells of diatoms of both discoidal 

 and naviculoid forms were also observed. 



Upon the foregoing facts the writer bases his conclusion that the 

 shad does feed in fresh water. 



If it were of any advantage, we might speculate ujjon the relations 

 subsisting between the smaller and larger aquatic and marine forms of 

 life, but perhaps enough has been said to show that there is an exten- 

 sive basis of fact to support what is imj)lied by the title of this paper. 

 The manifold adaptations and contrivances by which food is obtained 

 by organisms which prey upon others, and how the tendency to accu- 

 mulate the vast amount of the "physical basis of life," represented by 

 the existing Protozoa and Protophytes is practically realized by the 



