248 DESCRIPTION OF [Polygastrica. 



lorica, slightly three-lobed, and having a little process at 

 the posterior end. " I observed this species/ 5 says Ehren- 

 berg, " in phosphorescent sea-water from Kiel, and it is 

 very probable that the light proceeded from this animal- 

 cule. It is the smallest phosphorescent sea animalcule 

 that is known. Length l-600th to l-570th. 



376. PEBIDINIUM cornutum (Bursaria hirudinella, M.) 

 The horned Peridinium is of a greenish colour, not lumi- 

 nous ; its rhomboidal rough lorica has one, two, or three 

 straight horn-like processes in front, and a single one 

 (often curved) posteriorly. Length l-280th to l-140th. 



377- PERIDINIUM tripos (Cercaria tripos, M.) The 

 three-horned Peridinium is of a yellow colour, and very 

 brilliant in the night (phosphorescent). The lorica is 

 -urceolate, broadly concave, smooth, and three-horned; 

 the two frontal horns being very long and recurved, the 

 third, or posterior one, straight. Ehrenberg says, " The 

 power of this creature to evolve light is placed beyond 

 all doubt, as I took up a phosphorescent point nine times, 

 one after the other, from the water, and I saw nothing else 

 in each drop than a single animalcule of this species." It 

 is rigid, and swims with a vacillating rolling motion upon 

 the longitudinal axis. The length of the horns is not 

 constant, sometimes being scarcely as long as the body ; 

 at other times much longer. Figures 219 and 220 repre- 

 sent an under and side view. Found in the sea, near 

 Copenhagen and Kiel. Length 1- 140th; without the 

 horns, 1 -430th. 



378. PERIDINIUM Michaelis was discovered by Dr. Mi- 

 chaelis ; it is of a yellow colour, and intensely phospho- 

 rescent. The lorica is ovate, spherical, and smooth, with 



