Mar. 1832. 



PELAGIC ANIMALCULA. 



17 



again, a degree south of Valparaiso, the same appearance was 

 still more extensive. Although we were nearly fifty miles 

 from the coast, I at first attributed this circumstance to real 

 streams of muddy water brought down by the river Maypo. 

 Mr. Sulivan, however, having drawn up some in a glass, 

 thought he distinguished, by the aid of a lens, moving points. 

 The water was slightly stained as if by red dust ; and after 

 leaving it for some time quiet, a cloud collected at the bottom. 

 With a lens, of one-fourth of an inch focal distance, small 

 hyaline points could be seen darting about with great rapi- 

 dity, and frequently exploding. Examined with a much 

 higher power, their shape was found to be oval, and con- 

 tracted by a ring round the middle, from which line curved 

 little setae proceeded on all sides ; and these were the organs 

 of motion. One end of the body was narrower and more 

 pointed than the other. According to the arrangement of 

 Bory St. Vincent, they are animalcula, belonging to the 

 family of Trichodes : it was, however, very difficult to 

 examine them with care, for almost the instant motion 

 ceased, even while crossing the field of vision, their bodies 

 burst. Sometimes both ends burst at once, sometimes 

 only one, and a quantity of coarse brownish granular 

 matter was ejected, which cohered very slightly. The 

 ring with the setae sometimes retained its irritability for a 

 little while after the contents of the body had been 

 emptied, and continued a riggling, uneven motion. The 

 animal an instant before bursting expanded to half again 

 its natural size ; and the explosion took place about fifteen 

 seconds after the rapid progressive motion had ceased : in a 

 few cases it was preceded for a short interval by a rotatory 

 movement on the longer axis. About two minutes after any 

 number were isolated in a drop of water, they thus perished. 

 The animals move with the narrow apex forwards, by the aid 

 of their vibratory cilice, and generally by rapid starts. They 

 are exceedingly minute, and quite invisible to the naked eye, 

 only covering a space equal to the square of the thousandth 

 of an inch. Their numbers were infinite ; for the smallest 



VOL. III. C 



