272 GENERAL HISTORY OF THE INFUSORIA. 



Ciliated Protozoa, fii'st, because of their wreath or general clothing of cilia — a 

 phenomenon seen among none of the Phytozoa or Plagellata, which have never 

 more than one or two, or, rarely, four filaments or flabella ; and secondly, be- 

 cause every author who has described them treats them as animalcules. 

 Perty, although recognizing them as animals, nevertheless groups them with 

 his Phytozoidia, probably omng to their bizarre form and to the characteristic 

 internal organization of CiHata not being perceptible. Siebold, on the con- 

 trary, places them, together with Euglenwa and Opalincea, among the asto- 

 matous or mouthless Protozoa. 



Ehrenberg's description of the Peridinicea is as follows : — The animalcules 

 of this family are polygastric, but have no alimentary canal ; the mouth is 

 usually found in a depression near the middle, and from its vicinity a delicate 

 filament (proboscis) is given ofi' in three of the genera. They are clothed 

 with a shell or lorica, having a transverse furrow or zone occupied with a row 

 of vibratile ciha ; and besides this wreath, several species have also fine setae 

 or cilia scattered over them. In Peridinium acuminatum, P. fulvum, and P. 

 ( Ceratium) cornutum the digestive sacs are visible without recourse to artificial 

 means ; but in P. Pulvisculus and P. cinctum those organs can be demonstrated 

 only by the use of coloui-ed food, chiefly because they are hidden by the 

 clusters of ova, to which the colour of the animalcules is due. This is com- 

 monly red, yellow, or brown, and rarely green. In Peridinium Tripos and P. 

 Fusus a seminal gland (nucleus) is visilDle, and in Chcetoglena and Glenodinium 

 a red eye-speck. Longitudinal self-division has been observed in P. Pulvisculus 

 and P. Fusus. 



Dujardin, unable to accept these views of their organization, described the 

 ' Peridiniens ' as " animals without known internal organs, enveloped by a 

 definite resistant membranous lorica, which sends ofi' a flagelliform filament, 

 and has, in addition, one or more furrows beset with vibratile cilia. The 

 lorica would appear to have no orifice, since foreign particles and colouring 

 matters cannot enter it ... . The members of this family are distinguished 

 from Thecamonadina by the ciliated furrow or furrows." 



Further, Dujardin ignored the red stigma as a generic distinction, and in 

 this is followed by Perty. Ehrenberg created a subgenus of Peridinium for 

 those species which have the lorica prolonged into hom-like processes, under 

 the name of Ceratium. Both Dujardin and Perty retain this appellation, but 

 would elevate the group comprehended under it to the rank of a genus. 



Let us now proceed with a resume of the facts at present received respect- 

 ing the organization and habits of the Peridinio'.a. 



The lorica is double, consisting of an outer, more or less firm, non-contrac- 

 tile layer, and an inner, homogeneous, hyaline membrane : usually a space 

 occurs between the two coats ; but in Glenodinium they are in close apposi- 

 tion — a double contour, however, being perceptible. The inner layer may 

 be taken to represent the primordial utricle ; it immediately envelopes the 

 contents, which consist of a homogeneous protoplasm, enclosing within itself 

 numerous globules, granules, and vesicles. In the case of the smallest Peri- 

 dinicea, such as P. Pulvisculus, P. monadicum, and P. Corpusculum, the di- 

 stinctness of envelope from contents ceases, and when in a dying condition the 

 whole figure undergoes a great variety of changes — a fact indicating a less 

 perfect development of the lorica — and there is a rapid breaking up of the 

 contents. In the larger species the outer tunic is more elaborated, and either 

 displays a minute cellular or reticulate structure, or appears quite smooth and 

 structureless, although firm and resistant (as in Glenodinium cinctum). A 

 cellular lorica occurs in Ceratium, and also in various Peridinia, which Perty 

 separates from the rest, under the name of Glenodinium, by reason of this 



