27(5 On 



a remarkable Fish of the Family of Sturgeon 



column, and extend almost along the whole length of the abdo- 

 minal cavity, and arc everywhere separated, except at the hinder 

 end, where they coalesce. A small urine-bladder is provided 

 in front with two long spacious horns ; in a bladder 5 millims. 

 long the horns are 27 millims. long. The diameter of the roe 

 when nearly mature is about V6 millim. (from 1"3 to 1'8 

 millim.), the roe being of a brownish-yellow colour. In a 

 specimen 230 millims. long I counted in both ovaries about 

 1500 eggs. 



But the most interesting organ of our fish is its swimming- 

 bladder. It is quite rudimentary, a small bag-like appendage 

 to the stomach (in a specimen 235 millims. long the swimming- 

 bladder was 9 millims. long and 4*3 millims. wide), to which 

 it is joined by a short tube. This tube begins at the front 

 end of the bladder, and enters at the commencement of the first 

 stomach from the dorsal side at the distance of 1 millim. 

 from the end of the oesophagus. The position of the bladder 

 between the stomach and the vertebral column is normal ; 

 its walls consist of the same membranes as those of the first 

 stomach. 



For the cause of such a peculiar development or, rather, 

 malformation of the swimming-bladder in the Scaphirhynchas 

 Fedtschenkoi we must search, in all probability, in the mode 

 of life of this fish. There is no doubt (at least I think so) 

 that this fish is obliged to live continually at the bottom of 

 the river, and there burrows in the sand or mud in order to 

 get its food. This is evident from the shape and structure of 

 its snout as well as the smallness c^f its eyes, which have 

 become almost rudimentary. Indeed I found in the stomach 

 of our fish exclusively the remains of creatures living in mud. 

 It is known that the swimming-bladder is wanting in those 

 fishes only which are in the habit of living at the bottom of 

 the water (viz. rays, soles, lampreys, &c.). 



The fish described by us was discovered by M. A. P. 

 Fedchenko in the river Suir-dar. According to his notes the 

 native fishermen do not consider it to be a distinct species, 

 but merely look upon it as the young of the sturgeon of the 

 Aral Sea. Evidently they do so in consequence of its normally 

 small size. Out of the twelve specimens brought by M. 

 Fedchenko the largest were only 8^ inches long (exclusive of 

 the caudal filament) ; among them there were some females with 

 eggs almost completely matured. This is no doubt the reason 

 wliy this fish escaped the notice of former travellers who had 

 visited the banks of the river Suir-dar. 



