[15] AN INDIRECT SOURCE OF THE FOOD OF FISHES. 769 



small adult crane-fly, besides Entomostraca allied to Lynceus. In these 

 specimens the dorsal fin had the rays developed, the continuous median 

 larval natatory folds having by this time disappeared. 



The mode in which the young fish capture their Entomostracan prey 

 may be guessed from their oral armature. Most fish larvae appear to be 

 provided with small, conical, somewhat backwardly recurved teeth on 

 the jaws. Eathke, in 1833, described the peculiar hooked teeth on the 

 lower jaw of the larvae of the viviparous blenny, and Forbes has ob- 

 served minute teeth on the lower jaw of the young Goregonus albus. I 

 have also met with similar teeth on the lower jaw of the larval Spanish 

 mackerel. 



THE FOOD OF THE ADULT SHAD. 



The mouth of the adult shad, as is well known, is practically tooth- 

 less, and in the throat there are no functionally active teeth, as in the 

 larvae, so that the latter, in reality, have a relatively much better de- 

 veloped dentary system than their parents. The adult, moreover, prob- 

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

 say, by swimming along with the mouth held open, as I Lave 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 fishermen that it is seldom that one 

 finds food in the stomach of the adult shad in fresh water; 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 spawuing 

 season. With this unreasonable opinion I cannot coincide, and I hav^e 

 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. That it does probably capture large numbers of small 

 Crustacea in fresh water the following observation will show: A spawn- 

 ing 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 of these creatures. This was the invariable rule, even where there 

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

 S. Mis. 110 49 



