390 ANNUAL OF SCIENTIFIC DISCOVERY. 



and the pipe-fish, both having heads very much elongated anteriorly and 

 pointed. These fish sometimes pierce the stomach of the cod and escape 

 into the abdominal cavity, and there they arc found in a perfect state of 

 preservation, adherent to its walls, but changed in color to a dark red, and in, 

 substance so hard that they arc not readily divided with a knife. They have 

 to be cut away before the cod can be split open. The fish is always in good 

 health, apparently, and there are no marks of inflammation about the stomrwh 

 or abdominal cavity, unless the material of attachment be considered as such. 

 Fish migrate considerable distances in quest of prey, sometimes totally 

 deserting localities where they have been very abundant. There is a species 

 of crustacean called commonly by fishermen the sea-flea, which infests spots 

 upon the Grand Banks, hundreds of square miles in extent, and which drives 

 before it the cod and other fish. During his last voyage to the Banks, Cap- 

 tain Atwood tried to fish with clam bait, which, however, came up untouched ; 

 he then put on menhaden for bait and lowered to the bottom, but upon rais- 

 ing the hook nothing was found but the skeleton of the fish, the soft parts 

 having been consumed by the sea-flea. 



ARTIFICIALLY REARED FISH. 



At a recent agricultural and industrial exhibition, in Paris, about three 

 thousand fish were exhibited from the Artificial Piscicultural Establishment 

 formed at Thuringen by the French government. They consisted of salmon, 

 from the Danube, trout, from the lakes of Switzerland, and grayling from the 

 Lake of Constance. The last named were products of eggs hatched during 

 the spring of 1857. There were also salmon of three years, some of which 

 measured nineteen inches long by thirteen inches in circumference. These 

 fish were conveyed in cylindrical reservoirs made of tin, the water being 

 renewed frequently. 



It is tolerably well ascertained that the growth of artificially-reared fish, 

 particularly salmon, is less rapid than under ordinary circumstances. Left 

 to nature, the salmon will grow to about twenty-five pounds in three years ; 

 reared and fed at the piscicultural establishment at Thuringen, he will not, 

 in the same time, have reached a weight of five pounds. 



From information gained at the salmon-breeding establishment, in Scot- 

 land, it also appears probable that there is a very singular retardation in the 

 development, and that the young of salmon, under certain circumstances, 

 continue to hold their generic character for an indefinite period, instead of 

 assuming their last metamorphosis. The question, then, may be asked : Is 

 it then a law that of the ova of a single incubation a certain number become 

 fully developed after a residence in the fresh water of a. few weeks a cer- 

 tain number at the end of a year and a still greater number never, but, 

 retaining their generic dress, continue in this dwarfish state in the fresh- water 

 rivers ? 



INTERESTING PHYSIOLOGICAL RESEARCHES. 



The following is an abstract of a communication recently made to the 

 Boston Society of Natural History, by Mr. Brown Sequard. 



