280 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



Let us take a British enumeration of these organs in diiferent families, 

 having different habits, and requiring different food. "While there are 

 six in the smelt {Salmo eperlanus), there are seventy in the salmon {8. 

 salar). In like manner, though there are eighteen in the anchovy 

 {Glupea cncrasicolns), there are twenty-four in the herring (C Jiarcngiis), 

 and fourscore in the shad (C. alosa). In some, as in the cod, says the 

 same authority, they consist of several large trunks, ramihed into nu- 

 merous small ones. 



The herring and anchovy, though closely allied to the shad, are of 

 small size, and do not go far beyond brackish water to spawn. Hence 

 their coeca are few and small. The salmon, a fish of large size, has 

 fewer recei>tacles than the shad ; for the former can obtain, from day 

 to day, suitable food in the fresh waters it frequents. But the adult 

 shad, from the nature of its food. Is dependent upon that, in the liquid 

 state, which it brings with it from the ocean 5 and consequently its 

 pyloric appendages are numerous and long. 



In the cod, as was stated before, the coeca consist of several large 

 trunks ramified into numerous small ones. Now, as this is exclusively 

 a salt-water fish, the arrangement here would seem to be at variance 

 with the opinion expressed concerning the uses of these organs. But, 

 compared with the shad, the cod is of enormous size, and, though a salt- 

 water fish, it is highly probable that, for the most part, it migrates from 

 its feeding grounds to perform its reproductive functions in securer 

 oceanic localities than those in which it fattens. 



It is the shad, however, which occupies our attention. 



The distance from shore at which this fish can obtain its appropriate 

 food may be inferred from the botanical nature of the alg?e on which 

 they feed; and i)erhaps the shells of the infusoria may assist the search. 

 As a guide, the statement of Forbes should be regarded. 



"The British marine plants," says that author, "are distributed in 

 depth or bathymetrically in a series of zones or regions which ex- 

 tend from high- water mark down to the greatest explored depths" (for 

 plants). 



There are no waters more fertile in algse than those of the Gulf of 

 Mexico; and none in which the minute organisms, that fasten on marine 

 plants, are more numerous and varied. A cold aqueous belt, of vast 

 area — bounded on the south by the gulf-stream — almost isothermal with 

 that which washes the shores of Georgia and the Carolinas — extends 

 along the coast Jrom the mouth of the Mississippi to Cape Sable. 



Here may be found several species of alosa. One, from its size and 

 physical construction, and as an article of fooil, rises considerably above 

 insignificance. It is frequently caught in the headwaters of the rivers 

 of Alabama, where it spawns. But the shad of the Atlantic, a fish 

 affording, from its gregarious and prolific nature, a valuable food for man, 

 does not naturally exist in the Gulf ol Mexico. Yet there is much reason 



