768 EEPOET OF COMMISSIONEE OF FISH AND FISHERIES. [14] 



ture food to swallow aud digest, so that it may no louger be dependent 

 upon the store of food inherited from its parent. 



The appearance of the teeth. — Minute conical teeth make their appear- 

 ance on the lower jaws and in the pharynx of the young shad about the 

 second or third day after hatching. Sections through the heads of em- 

 bryos show that these teeth are derived from the oral, hypoblastic 

 liniug of the mouth. There are none on the ui^per jaw; there are four 

 arranged symmetrically on the lower jaw, or rather Meckel's cartilage. 

 In the throat, in the vicinity of the fifth and last branchial arch, there 

 are two rows of lower pharyngeal teeth, the first of six, three on a side; 

 the last of four, two on a side. These teeth are of the same form and 

 size as those on the jaws. 



The age at ichich it begins to tal^e food. — Although peristaltic contrac- 

 tions of the walls of the intestine of young shad may be observed soon 

 after hatching, I have never observed food in the alimentary canal 

 until ten or twelve days after the young fish had left the egg. At about 

 the beginning of the second week considerable may be seen in living 

 specimens. But the intestine is often not yet very densely packed with 

 food even at this period. At the age of three weeks an abundance of 

 food is found in the intestine, that portion which becomes the stomach, 

 and which extends from the posterior extremity of the liver to near the 

 vent being greatly distended with aliment. 



Upon investigating the nature of this food material we learn that it 

 consists almost entirely of exceedingly small crustaceans, in reality for 

 the most part of the very youngest Daphniadw and Lynceidce ; only once 

 did I find what I thought might be very small Ostracoda or Ci/pridce. 

 In some instances the undeveloped larvae of Daphnice were noticed. In 

 a few cases green cellules were observed in the intestines of shad larvae, 

 resembling Protococcus, but as this material appeared to be accidental 

 it is probably not an important element of shad food. In the young 

 fishes the dark, indigestible remains of the food of the Daphnice always 

 remained, together with the hard chitinous parts, as long-curved cylin- 

 drical casts which preserved the shape of the intestines of the crusta- 

 ceans. In one young shad, twenty-two days old from the time of im- 

 pregnation, measuring 14 millimeters in length, I estimated from a 

 series of sections through the specimen that it must have consumed 

 over a hundred minute crustaceans. 



The oldest specimens of artificially reared shad which came into my 

 hands were some that had been overlooked in some of the hatching 

 apparatus at Dr. Capehart's fishery in North Carolina, where they re- 

 mained for three weeks after hatching. In that time they had grown 

 to a length of 23 millimeters, or almost one inch. The air-bladder was 

 more developed and the stomach was more decidedly differentiated 

 than in any j)revious stage. In the intestines of these I found, beside 

 black, earthy, and vegetable indigestible matter, the remains of the chit- 

 inous coverings of small larval Diptera, and the remains of a very 



