770 KEPORT OF C0MM18SI0>'EK OF FISH AND FISHEEIES. [16] 



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 upon the relations 

 subsisting between the smaller and larger aquatic and marine forms of 

 life, but i)erhaps enough has been said to show that there is an exten- 

 sive basis of fact to support what is implied 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 

 hordes of Entomostraca and other small animals with which both fresh 

 and salt waters teem. How these again are accumulated in apprecia- 

 ble quantities so as to furnish an important source of food is shown by 

 the immense numbers, amounting to many thousands, which may be 

 taken from the stomach of a single fish. In the case where the large 

 quantity of Copepoda was obtained Irom the stomach there were ]>rob- 

 ably more than 100,000 individuals of these crustaceans, which would 

 average a fifteenth of an inch long and a fiftieth of an inch wide. This 

 fact will serve to show how fine the meshes of the branchial sieve must 

 be to prevent the prey of the shad from escaping from this remarkable 

 collecting apparatus. The soft parts, too, of the individual crustaceans 

 were so well preserved that one could distinguish the pigment of the 

 eyes, the muscles, and intestine with its contents, while the vast num- 

 ber of their eggs mixed amongst their bodies testified to the multitudes 

 of females which had been swallowed. These facts would appear to in- 

 dicate most positively that the fish had captured its food quite recently 

 and after it had reached quite fresh water. 



