576 



SYSTEMATIC HISTORY OF THE INFUSORIA. 



or furrow, but striped or covered with spines or stiiF hairs, and ha\ing an 

 eye-speck. The organ of locomotion is a simple iiabellura. The interior 

 contains scattered transparent vesicles, and a brownish-green granular mass ; 

 a large bright spot or nucleus is also \dsible. Self-division not observed. 



CiL^TOGLENA volvocma. — Ovate, with 



browmish-gTeen granules, and a red eye ; 

 between tlie lorica and the soft body a 

 beautiful red ring is visible in live spe- 

 cimens (x. 216, 218). Amongst Confer- 



vas at Hampstead and Hackney. 1-1150". 

 C. cauclata. — Hispid, ovate, with a 

 short tail ; granules green ; ocellus clear 

 red ; oral margin urceolate and dentate. 

 1-864". Berhn. 



Genus PEE.IDIjS'IUM. — Lorica membranous, with a transverse ciliated 

 zone ; no eye. The locomotive organs are a filament and the zone of cilia. 

 In P. Pulvisculus and P. cinctum, indigo and carmine are received, and de- 

 monstrate the formation of vacuoles, which in P. acuminatum, P. fulvum, 

 and P. cornutum are visible ^dthout having recoiu'se to colonized food. The 

 oral aperture is found in a hollow near the centre, as in Bursaria. The 

 granules are generally of a brown or yellowish-brown colour, though some- 

 times green or even almost colourless. In P. Tripos and P. Fusus an 

 oval nucleus is visible. Self-di\'ision is longitudinal in P. Pulvisculus and 

 P. fuscum ; and, according to some observers, transverse in P. Fusus and 

 P. Tripos. 



The structural peculiarities are sufficiently described in the chapter on 

 Peridiniaea (p. 271). The existence of a mouth and the entrance of food are 

 still matters of doubt. A nucleus is probably present in all ; and the same 

 may be said of the llabellum, which subsequent observers have distinctly 

 found in cases where it eluded the observation of Ehrenberg. " Fossil Peri- 

 dhiia/^ says Perty, " are not found in recent geological formations, but only 

 in the chalk bed^ of the secondary strata, in which they occur with Xan- 

 tliicUa (Ehr.) and PyxidicuJoi.'" 



a. Peridinia luithout horns. — Peribinium. 



Peridinium cinctum ( Vorticella cincta, 

 M.). — Nearly globular, or slightly three- 

 lobed and smooth, with a zone of cilia ; 

 not luminous. It swims slowly, with a 

 vacillating and rolling motion. Amongst 

 Coufervpe. 1-570." 



Instead of the red zone noted by Ehren- 

 berg, there may be only a single speck, 

 or even it may be absent. 



P. Pulvisculus. — Small, of a brown or 

 gi'eenish-yellow colour, and not lumi- 

 nous ; almost spherical, or slightly three- 

 lobed ; a fine filament 2i lines longer 

 than the body may be observed ; nume- 

 rous vacuoles produced by feeding on in- 

 digo. Amongst Conferva), with Cldami)- 

 domonas Pulvisculus. 1-2300" to 1-1150". 



Perty has met with specimens having 

 a red speck. 



P. fuscum. — Is not luminous; oval, 

 slightlv compressed and pointed ante- 

 riorly.' 1-430" to 1-280". 



P.' Monas. — Very small, obtuse, with- 

 out horns ; remarkaljlv social. Diam. 

 1-1728". In the Baltic. 



Pertv suffg-ests that this is merely a 



young stage of P. ( Ceratium) cornutum. 



P. Planulum (Perty). — Rounded, broad, 

 rather compressed; the two segments 

 equal. Colom* brown, usually a deep tint. 

 Under surface rather concave. 1-720" to 

 1-430". Its brown contents contract 

 after death into a central lump. A red 

 speck is often seen in the posterior por- 

 tion. It is distinguished from Glenodi- 

 iiium cinctutn by its greater width and 

 deeper colom*. 



P. Corjmsculum (Perty). — Small ; seg- 

 ments very unequal, posterior one very 

 short and cleft. Granular contents 

 bro^^Tiish-yellow, or red or green. An 

 alteration in figure has been seen to 

 ensue after death. 1-1120". Amongst 

 3Iarchantia poli/morpJia. 



P. momulicum (Perty). — Very small; 

 segments unequal, the posterior one 

 much smaller ; with red stigma in the 

 line of constriction, more seldom in the 

 hinder half Molecules pale green. It 

 is the smallest known example in this 

 family. 1-1150". In a pond on Mount 

 St. Gothard and at Bern. 



