120 STURGEONS. 



internal side, to the parietes of a membranous canal. Remark- 

 able modifications in the mode of organization of these organs 

 are observed. Sometimes the branchiae are free on the external 

 edge, as in the osseous fishes ; sometimes, on the contrary, they 

 are attached by both edges, and this difference furnishes a basis 

 for the division of cartilaginous fishes into two groups : the 

 Chondropterygians with free branchiae, which constitute a single 

 order, and the Chondropterygians with Jlxed branchiae^ which 

 form two orders, the Selachii, and Cyclostomi. 



ORDER OF CHONDROPTERYGII BRANCHIIS LIBERIA 

 OR STURIONES. 



2. The Sturiones, or Chondropterygians with free branchiae, 

 of which the Sturgeon is the type, resemble ordinary fishes in the 

 disposition of their gills, as well as in their free branchiae ; they 

 have, on each side, a single branchial opening, furnished with an 

 operculum, but which wants the rays. 



3. The STURGEONS, Jlcipenser, have the general form of 

 osseous fishes, and, in the structure of their skeleton, form the 

 connecting link between them and the Chondropterygians; 

 for many bones of their head and shoulders are completely 

 hardened and, as it were stony on the surface. Their upper 

 jaw is composed of the palate bones solidly attached to the maxil- 

 lary bones, and vestiges of intermaxillary bones are found in the 

 substance of the lips. The body is more or less covered with 

 plates imbedded in the skin in longitudinal rows ; their mouth is 

 small and unprovided with teeth ; the dorsal fin is situated be- 

 hind the ventral, and above the anal fin ; the caudal fin surrounds 

 the extremity of the tail, and has a projecting lobe beneath. 

 These fishes are generally large, and endowed with very con- 

 siderable muscular strength : they easily stem the most rapid 

 current, and can strike violent blows with their tail ; but their 

 habits are ordinarily peaceful, and they are formidable only to 

 small, or badly armed fishes ; they feed on herrings, mackerels, 

 sometimes salmons, and they have been seen to root in the mud 

 with their nose, in pursuit of worms and mollusks. In the spring 

 they ascend certain rivers from the sea, often in numerous shoals, 

 to deposit their eggs. Their fecundity is very great ; we are 

 assured that 1,500,000 eggs have been found in one female that 

 weighed 278 pounds, and in another, weighing 2800 pounds, the 

 eggs by themselves, weighed 800 pounds. The young ones 



2. What are the characters of the Sturiones ? 



3. What are the characters of Sturgeons ? What is Caviar ? What is 

 Ichthyocolla? 



