516 DESCEiPTioN ov {Polygastricu. 



and P. cinctmn the digestive apparatus can be dcmonsti'ated, by em- 

 ploying indigo and carmine as food ; but in P. acuminatum, P. fulvum, 

 and P. cornutum, it is visible without having recourse to artificial 

 means. The oral aperture is found in a hoUow near the centre, as 

 in Bursa/i'ia. The ova cluster is generally of a brown or yellowish- 

 brown colour, though sometimes green, or even almost coloiuiess. 

 In P. tripos, and P. fusus an oval seminal gland is visible. Self- 

 division is longitudinal in P. pulvisculus and V.fusciim ; and, according 

 to some observers, transverse in T. fusus and P. tripos. 



(a). Wreath Animalcules without horns. — PEEiDiNrcrM. 



Pehtuinium cinctum {Vorticella cincta, M.)— Is nearly globular, or 

 slightly three-lobed and smooth, with a zone of ciHa ; it is not 

 luminous at night. It swims slowly, with a vacillating and rolling 

 motion. Pound amongst Conferva. Size 1 -570th. 



p. ptdviscuhts. — Small, of a brown colour, and not luminous at 

 night ; lorica almost spherical, or slightly three-lobed ; a delicate 

 proboscis may be observed, as well as numerous stomach-cells, by 

 feeding it on indigo. Foimd with Chlamidomonas puhisculus- Length 

 l-2300th. to l-1150th. 



P. fusciim.—ls not luminous at night ; the lorica is oval, slightly 

 compressed and pointed anteriorly. Length 1 -430th. to l-280th. 



(i). Wreath Animalcules with horns. — Ceeatium. 



P. (?) pi/rophorum. — Lorica ovate, spherical, with two little points 

 at its anterior extremity. It is very delicately m'ceolate and granu- 

 lar. Pound fossil in the flints of the chalk formation at Berlin. 

 Size 1 -570th. to l-480th. 



P. (?) Delitiense. — Lorica ovate, spherical ; with a little stiff 

 point near the middle laterally. Fossil in the flints of Delitzsch. 

 Size 1 -430th. to 1 -280th. 



P. acuminatum.— Qoloux brownish -yellow ; lorica ovate, spherical, 

 slightly three-lobed, and having a little process at the posterior end. 

 " I observed this species," says Ehrenberg, " in phosphorescent 

 sea- water from Kiel, and it is very probable that the light proceeded 

 from this animalcule. It is the smallest phosphorescent sea animal- 

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



P. cornutum (Bursaria hirudinella, M. Ceratium hirudinella. 



