514 



SYSTEMATIC HISTOEY OF THE INFUSORIA. 



a reddish glimmer ; possilily a contrac- 

 tile vesicle ; movements slow ; no con- 

 tractions of fig-ure observed. Botli ends 

 fumislied with delicately motile fila- 

 ments, those on the anterior longer 



than those on the posterior extremity; 

 but still seen with difiicult3\ In swim- 

 ming it lies on the flat surface ; it also 

 revolves on its long axis. 1-15'" to 1-14'". 

 In water from Walldorf. 



FAMILY IV.— YOLYOCINA. (See p. 144.) 



(XIX. 32-69 ; XX. 22-47). 



This family derives its name from the genus Volvox, and from the rolling 

 motion with which the beautiful creatures belonging to it make their way 

 through the water. They resemble the Monads in most particulars relating 

 to their organization ; have an unvai^jing form, and, except a filament, no 

 appendages ; vacuoles present. ^Tiilst propagation by self-division is pro- 

 ceeding, and the young are increasing in size, the suiToundiug envelope or 

 lorica is observed to expand in a corresponding degree, but continues entire 

 until its numerous occupants have come to maturity, when it bursts and sets 

 them at liberty. 



All the genera are provided with organs of locomotion, which consist, as 

 ^ith the Monads and Cryptomonads, of a single or double very delicate fila- 

 ment ; and hence it is that when they are clustered, the entire grouji appears 

 to be cihated, or beset with hairs. Besides granules, one or two round nuclei 

 and a contractile sac are present. 



This family Ehrenberg disposed into ten genera — five ftimished with a red 

 stigma, situated at the anterior part of the body, and five without it. In the 

 former, a sensitive system was presumed on the supposition of the red speck 

 being an eye. 



The following is an analysis of the family : — 



Tail 



absent | 



( 



\'ibrating 

 filament absent 



Lorica box-hke 



i Gyges. 



Lorica single * 



j vibrating ^ 

 l^ filament present J 



Pandorina, 





Clusters tabulated or in plates Gonium. 



^ Lorica double Syncrypta. 



Tail present Synm-a. 



(^ Tail present Uroglena. 



Self-division both j 



equal and perfect \ { filament single . . . Eudorina. 



(no internal globes) Tail absent 



filament double . . . Clilamydomonas. 



{ Filament single Sphterosira. 

 Filament double Yolvox. 



The above account, derived from Ehrenberg's work, afifords a very imperfect 

 conception of the Yolvocina, especially of their structui-al characteristics as a 

 family, — a defect we have endeavoured to supply in the chapter on their 

 general history (p. 144). Moreover, as there noticed, these beings are 

 numbered by the majority of naturalists, at the present day, among plants, 

 although a respectable minority, among whom are Thiu^et and Laehmann, 

 incline to the opinion that they are for the most part animals, as Ehrenberg 

 represented. Thuret expressed this opinion now several years since, when 

 the physiology of the simplest vegetable organisms was imperfectly imder- 



