574 SYSTEMATIC IIISTOEY OF THE INFUSOEIA. 



FAMILY II.— PEEIDINIJEA. (Part I. p. 271.) 

 (PL X. 214-226 ; XII. 47 ; XXXI. 16-23.) 



Infusoria without an alimentary canal, covered with a lorica, upon which cilia 

 or setae are often arranged in the form of a zone or crown — hence the name. 

 The lorica has only one opening. Three out of the four genera have a fila- 

 ment besides the wreath of ciHa around the middle of the body, or scattered 

 cilia or bristles. In only Peridinium Pulvisculus and P. cinctum have artificial 

 means succeeded in demonstrating the admission of food, the internal organi- 

 zation being greatly obscui^ed by the mass of coloiured opake granules, which 

 Ehrenberg called ova. A nucleus and a red stigma (eye, Ehr.) are discover- 

 able in some species. 



The genera are disposed as follows : — 



Lorica having stiff bristles or short spines — no transverse J ^ ^" 



fiuTOwed zone | eye present Chsetoglena. 



T . ^, , -1 • ^ 1 ^ f no eye Peridinium. 



Lorica smooth or rougli — a ciliated transverse zone pre- ' "^ 



^®^*' • I eye present Glenodinium. 



Some of the presumed species have been found only in a fossil state in flint. 



Dujardin constitutes a family Peridiniens, agreeing in the main with that 

 of Ehrenberg, and thus narrates its characters: '' Animals without known 

 internal organs ; enveloped in a regular, resistant, membranous lorica, which 

 sends off a long flageUiform filament, and, in addition, has one or more furrows 

 beset with vibratile cilia." 



The lorica would appear to have no opening ; for foreign bodies and colour- 

 ing matter are not seen to enter it. Several have theii^ lorica prolonged into 

 horn-like processes ; and some exhibit a coloured point (eye-speck). They 

 are distinguished from Thecamonadina by the ciliated furrow or fuiTOWS. 



Dujardin observes that " as the first two of Ehrenberg's genera are with- 

 out the furrow and vibratile ciha, and have only a filament as a locomotive 

 organ, they are evidently akin to, and not separable from the Thecamonadina, 

 unless spines or asperities of the lorica are to be taken for cilia. Again, the 

 so-caUed eye-speck is not a sufficient generic distinction between Peridinium 

 and Glenodinium ; the former genus, moreover, should only include spherical 

 animalcules, whilst those concave on one side, and exhibiting horns, will 

 rightly form a distinct genus — Ceratium.^^ 



Perty coincides with Dujardin in detaching Chcetotyphla and Chcetoglena 

 from the Peridinigea, and in uniting them with Thecamonadina. OhcetogJena 

 he merges with Pantotrichum and LageneUa in a genus which he names Chone- 

 monas (p. 513). His Peridiniaea comprehend three genera, viz. Ceratiwn, 

 Glenodinium, and Peridi^iium: the first characterized by a cellular lorica 

 prolonged into horns ; the second by a ceUular not-horned lorica ; and the 

 third by a structm-eless lorica. A reference to the figures of Chcetoglena and 

 Chcetotyphla is sufficient to show that these two genera have no claim to be 

 ranged with Peridiyiium : the former, in particular, indicates in its structure 

 and general appearance a member of the Cryptomonadina ; and the latter, if 

 not a member of the same order, is certainly not one of the Peridiniaea, but 

 probably the encysted state of some animalcule. The imperfect descriptions 

 attached to these genera, and the absence of sufficiently distinctive features 

 in their illustrations, renders their exact identification with similar known 

 forms a matter of difficulty, if not of impossibility. Again, the special differ- 



