538 ■ SYSTEMATIC HISTOEY OF THE INFUSOEIA. 



In Ehrenberg's system the family Closterina follows here, but in this edi- 

 tion it is transferred to the Desmidieae, of which it constitutes an important 

 genus. (See Part I. p. 1 et seq.) 



FAMILY VI.— ASTASLEA oe EUGLEN^A (see p. 188). 



(XYIII. 35-56 ; XX. 15-21). 



The members of this family are, according to Ehrenberg, characterized by 

 being deficient of a true alimentary canal and lorica, and by having a single 

 aperture and the power of changing their form at pleasiu'e. Theii^ organs 

 of locomotion consist of a tail in most cases, a single filament in three genera, 

 and a double one in a fourth. It is probable that filaments exist also in the 

 other two genera, Colacium and Distigma. The internal vesicles were pre- 

 sumed to be gastric sacs, although the usual test of their being so, viz. the 

 application of coloured food, failed in Ehrenberg's hands ; yet, he says, he 

 noticed some manifestations of a digestive power in the green and red cells of 

 Euglena viridis. In Euglena there are, besides green ova (granules), a gland 

 (nucleus) and a contractile vesicle ; but Astasia, Distigma, and Colacium ex- 

 hibit only ova. Large red points are found in five genera. In Euglena 

 longicauda and E. amhlyophis, adds Ehrenberg, " the first indication of the 

 presence of nervous matter to be found in the polygastric Infusoria " is met 

 with in the form of a white glandular knot, situated below the eye. 



The following table illustrates the characters of the genera of this family 

 as instituted by Ehrenberg : — 



Eye wanting 



Eye present 



Free 

 With one eye 



With one f ^^"^ wanting Amblyopliis. 



proboscis I ^^.j ^^^^^^^^ Wxglen^. 



^ With two proboscides Chlorogonium. 



(^ Attached by a pedicle Colacium. 



^ With two eyes Distigma. 



The family Euglenaea (Eugleniens) of Dujardin in a great measure corre- 

 sponds Avith that of Astasiaea of Ehrenberg; but Dujardin prefers the term 

 Euglenaea, on account of the resemblance of the other name to that of a 

 family of Crustaceans, viz. the Astaciaea. 



Dujardin looks upon the so-called eyes as insufficient to afford generic 

 characters, which he would derive from the nature or apparent structure of 

 the integument, and the number and mode of insertion of the filaments. On 

 these principles he establishes a genus Polyselmis, characterized by its many 

 filaments ; two genera, Zygoselmis and Heteronema, by a paii' of filaments, in 

 the former of equal, in the latter of unequal size. The remaining Euglenaea, 

 which have but a single filament, can be but uncertainly defined : such are 

 the Euglena^, mostly coloured, and having a red eye-speck and a tail ; the 

 Astasice without colour and tail, but with a filament flexible throughout, and 

 springing abruptly from a notch in the anterior extremity ; and the PeranemcB 

 only diff'ering from the Astasice. in having a filament rigid at the base, and 

 apparently a continuation of the tapering anterior extremity of the animalcule. 

 The two last genera are, however, but provisional. 



Astasiaea is one of the families in the group of Phytozoidia of Perty, who 

 ignores the genera Amhlyopliis and Distigma of Ehrenberg, adopts the Pera- 

 nema and Zygoselmis of Dujardin, and adds, as new genera, Eutreptia and 



