GENUS COLPIDIUM. 537 



an ovate undulating membrane, its left one ciliatc ; the posterior extremity 

 of the body usually bearing supplementary setose cilia. 



Lembadion bullinum, Perty. PL. XXVII. FIG. 54. 



Body ovate, compressed, nearly twice as long as broad, slightly widest 

 posteriorly ; oral fossa capacious, extending through two-thirds of the entire 

 length of the body; two long hair-like setse projecting from the posterior 

 extremity ; endoplast spherical, posteriorly located ; contractile vesicle 

 single, situated near the centre of the right lateral border. Length 1-240" 

 to 1-192". HAB. Marsh water. 



This species was formerly referred, even by Stein, to the family of the Bursarina, 

 the undulating membrane which that authority has since demonstrated to exist 

 within the oral fossa being then regarded as a fringe of larger adoral cilia. For such 

 larger adoral cilia this membrane has likewise been mistaken by Claparede and 

 Lachmann, who have consequently placed it in their treatise next to the genus 

 Bursaria. These last-named investigators remark that under disturbing or uncon- 

 genial influences the animalcules of this species swim rapidly backwards, turning 

 upon their long axis, while, when seeking for food or moving at leisure, they 

 progress slowly forwards without any revolving action. Ernst Eberhard* represents 

 this type as bearing three postero-terminal setae. 



Doubtful Species. 



The Lembadion (?) duriusculum of Perty is a doubtful form, certainly not referable 

 to the genus under notice, and whose exact relationship cannot at present be decided. 

 Its diagnosis, as given by Perty, is as follows : Body persistent in form, elliptical, 

 colourless, with usually a keel or ridge along its upper surface ; the under surface 

 somewhat concave ; cilia very fine ; movements sluggish. Length 1-720" to 1-620". 

 HAB. Fresh water. 



GENUS VI. COLPIDIUM, Stein. 



Animalcules free-swimming, entirely ciliate, persistent in form, more of 

 less kidney-shaped ; oral aperture inferior, subterminal, pharynx supporting 

 throughout its length an undulating membrane which projects exteriorly 

 in a tongue-like manner. 



Colpidium cucullus, Schrank sp. PL. XXVII. FIG. 49. 



Body kidney-shaped, narrower 1 and curved towards the ventral aspect 

 anteriorly, two or three times as long as broad ; cuticular cilia distributed 

 in even longitudinal rows ; endoplasts two in number, rounded, subcentral ; 

 contractile vesicle located near the centre of the dorsal border. Length 

 1-500" to 1-250". HAB. Fresh water and infusions. 



This species was first figured and described by Schrank, 'Fauna Boica,' 1803, 

 under the title of Colpoda cucullus. It is identical with the Parameaum kolpoda of 

 Ehrenberg, and Claparede and Lachmann, and with the Kolpoda cucullus of Dujardin, 

 but not with the Colpoda cucullus of Ehrenberg, which is a more simple-formed 

 animalcule, having a conspicuous tuft of oral cilia but no vibratile membrane. 



* ' Osterprogramm zu Coburg,' 1862. 



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