8 NATURAL HISTORY. 



the sides of rocks, being as it were a large but tough 

 moss. It is the more to be noted, because that there 

 be but few substances, plant-like, that grow deep with 

 in the sea ; for they are gathered sometimes fifteen 

 fathom deep : and when they are laid on shore, they 

 seem to be of great bulk ; but crushed together, will 

 be transported in a very small room. 



Experiment solitary touching sea-fish put in fresh 

 waters. 



703. It seemeth that fish that are used to the salt 

 water, do nevertheless delight more in fresh. We see 

 that salmons and smelts love to get into rivers, though 

 it be against the stream. At the haven of Constanti 

 nople you shall have great quantities of fish that come 

 from the Euxine Sea ; that when they come into the 

 fresh water, do inebriate and turn up their bellies, so 

 as you may take them with your hand. 1 I doubt there 

 hath not been sufficient experiment made of putting 

 sea-fish into fresh-water ponds and pools. It is a thing 

 of great use and pleasure ; for so you may have them 

 new at some good distance from the sea : and besides, 



1 Sandys, p. 23. Modern experience has confirmed what Sandys here 

 relates; but there is no reason to suppose that the fish have any enjoyment 

 in the state of half insensibility which the change to fresh water produces. 

 The cause is probably to be sought in what appears a priori to be certain, 

 namely, the rapid absorption through the gills of fresh water. All the con 

 ditions appear to be present by which absorption by endosmosis is occa 

 sioned. The periodical migrations from salt to fresh water, and vice versa, 

 of certain kinds of fish may perhaps be connected with a change in the 

 composition of the blood, determining endosmosis or exosmosis through the 

 gills, and consequently rendering the fish uneasy in its actual position. 



Has it ever been suggested that the persevering way in which salmon 

 ascend rapid streams may result from the unequal velocity of the water at 

 different depths ? The consequence of this variation would be a sensation 

 of greater pressure against the lower part of the body than on the upper; 

 which under certain circumstances may be agreeable. 



