4o6 ORDER FLAGELLATA-EUSTOMATA. 



Genus VII. UVELLA, Ehrenberg. 



Animalcules united by their posterior extremities and forming social, 

 free-swimming, spheroidal colonies, the individual zooids not enclosed 

 within a membranous lorica, nor the colony as a whole immersed within a 

 common gelatinous matrix or zoocytium ; flagella two in number, subequal ; 

 endoplasm containing two lateral colour-bands ; an eye-like pigment-spot 

 present or absent. Hab. — Fresh water. 



The non-possession of a separate membranous investment or lorica by the 

 animalcules of this genus serves to distinguish it from Synura. 



Uvella virescens, Ehr. Pl. XXII. Figs. 24-26. 



Bodies elongate-ovate or clavate, their united posterior extremities 

 attenuate and stalk-like ; flagella equal or subequal, exceeding the body 

 in length ; lateral pigment-bands bright yellowish-green, extending on 

 each side through almost the entire length of the body ; no conspicuous 

 eye-like pigment-speck ; contractile vesicles two in number, posteriorly 

 located ; endoplasm subcentral ; colony-stocks containing from five or six 

 to as many as seventy or eighty zooids. Length of bodies 1-2000". 



Hab. — Pond water. 



The posterior location of the contractile vesicles, independently of the absence of 

 separate loricre, serves at once to distinguish the zooids of this species from those of 

 Syniira uvella, with which in their aggregate condition they may otherwise be readily 

 confounded. The endoplast, akhough not distinctly exhibited under ordinary 

 conditions, is, according to Butschli,* at once defined by the application of Beale's 

 carmine. Encysted individuals possessing a delicate or irregular outer coat and a 

 denser internal one, were encountered by this authority both in connection with the 

 motile colonies and with the isolated animalcules. Longitudinal fission according 

 with that of the ordinary Flagellata was likewise noticed. 



Genus VIII. CHLORANGIUM, Stein. 



Animalcules more or less ovate, persistent in shape, exhibiting two 

 distinct phases of existence, the one motile and the other sedentary ; in 

 the former instance possessing two evenly developed, anteriorly inserted, 

 vibratile flagella ; in the latter condition non-flagelliferous, attached in social 

 groups, mouth downwards, to a common pedicle ; endoplasm enclosing two 

 lateral colour-bands ; contractile vesicle and endoplast conspicuous. 



This genus is instituted by Stein for the reception of the Colacium sientorinum 

 of Ehrenberg, which he reports as differing from the several species of Colacium 

 previously described in the possession by the motile zooids of two flagellate appen- 

 dages, a more or less firm and non-contractile cuticula, and in the development of 

 two lateral coloured pigment-bands. Probably, as demonstrated by the present 

 author in the case of Colacium Stcinii, it will be ultimately shown that the flagella 

 here also are retained during the sedentary condition. 



* •' Studien iiber Flagellaten," ' Zeitschiift fiir Wissenschaftlicher Zoologie,' Bd. xxx., 1878. 



