362 



EAMBLES OP A NATUEALIST. [Oh. XXI. 



of Hydrozoa pointed out some curious facts from which 

 interesting deductions might be made. Thus, while passing 

 through the Indian Ocean, in lat. 13° N., during an entire 

 day (March 17), we passed through shoals of Aureha, meeting 

 from time to time patches in which they were too numerous 

 to be counted, and in each of which there were many hundreds. 

 A noticeable fact I remarked with regard to them, was 

 that, without any exception that I could discover, these 

 Aurelise were, during the whole day, swimming in the same 

 direction, or with the wind. We were steaming nearly due 

 east, and a breeze was blowing a little south of east, and 

 the umbrellas were all inclined one way, and pointing in the 

 direction towards which the wind was blowing. 



On another occasion, in a dead calm, on a beautiful day, 

 off the river Min, I observed great numbers of a large white 

 species. The edges of the umbrella were frilled, and nu- 

 merous long and delicate threads stretched out straight and 

 parallel'; but what struck me as singular was, that these 

 threads did not aU iloat in the same direction, as though 

 drifted from the animal by wind or tide ; but although they 

 were several feet long, they formed three or four distinct 

 bundles, which stretched out straight, but in different and 

 often opposite directions from the body of the animal, from 

 which it appeared that they were propelled by a voluntary 

 effort. 



In passing through Banka Strait, owing to the number of 

 rivers (the Palembang and others) which flow out of the 

 island of Sumatra, the water was found to possess only 

 seven-tenths of the saltness of the ocean; but notwith- 

 standing this comparative freshness, I observed a number 

 of large white Ehizostomas floating just below the surface, 

 and apparently unaffected by this peculiar condition. 



