166 THE SEA. 



bringing the floating organisms to the gaping stomach. 

 There are, moreover, lower forms than these, but of 

 kindred structure and appetites, as the Tunicate Mol- 

 lusca, which devour immense multitudes of micro- 

 scopic creatures ; and these tribes are numerous and 

 varied. Some of these are free rovers in the ocean, 

 as the Salpadce, and these occur in hosts only less 

 wonderful than the Diatoms themselves. 



Dr Wallich speaks from his own experience, con- 

 firmed, however, by many other observers, when he 

 says, that between the Cape of Good Hope and St. 

 Helena, for many degrees of latitude, the ship passed 

 through vast layers of sea water so thronged with the 

 bodies of a species of Salpa as to present the consist- 

 ence of a jelly. These layers extended for several 

 miles in length. Their vertical depth it was impos- 

 sible to ascertain, owing to the motion of the ship. 

 They appeared, however, to extend deep ; and in all 

 probability were of a similar character to the immense 

 aggregations of close-packed swimming invertebrata 

 so well known to mariners in Arctic regions under the 

 appellation of "whale-food/' Each of thQse Salpce 

 measured about half an inch in length ; but so close 

 was their accumulation, that of the quantity collected 

 by a sudden plunge of an iron-rimmed towing-net, 

 lialf the cubic contents, after the water had drained 

 off, generally consisted of nothing but one thick gela- 

 tinous pulp. 



The stomach in these translucent and generally 

 colourless creatures forms a minute, opaque, yellow 



