GENUS MESODINIUM. 635 



Strombidium viride, Stein. 



Body obovate, obtusely conical anteriorly ; parenchyma coloured green 

 by the presence of innumerable enclosed chlorophyll-granules ; peristome 

 produced backwards as in Strombidium acuminatum, the ventral aspect 

 not having a supplementary row of fine cilia as in that species ; the cuticle 

 containing numerous minute staff-like bodies whose nature was not ascer- 

 tained, but which probably correspond with the trichocysts that form an 

 equatorial girdle in 5. Butschlii. Dimensions unrecorded. 



HAB. Fresh water. 



Strombidium caudatum, From. 



Body ovate, tapering posteriorly, and terminating in an elongate caudal 

 filament ; contractile vesicle posteriorly situated. Length, without filament, 

 i-iooo". HAB. Fresh water. 



But for the posterior location of the contractile vesicle, the author is disposed, 

 from the figure and brief description given by De Fromentel, to regard this type as a 

 Vorticdla detached, with its pedicle, from its fulcrum of support. 



Strombidium globosum, From. 



Body spherical, transparent ; ciliary wreath very small and inconspi- 

 cuous ; contractile vesicles large, two in number, posteriorly located. 

 Length 1-800". HAB. Fresh water. 



GENUS III. MESODINIUM, Stein. 



Animalcules free-swimming, ovate or pyriform, the anterior extremity 

 prolonged in a snout-like manner, and perforated apically by the oral 

 aperture ; bearing between the snout-like prolongation and more inflated 

 posterior portion of the body a circular fringe of setose or cirrate locomotive 

 cilia. Inhabiting salt and fresh water. 



The representatives of this genus appear to unite the characters of Halteria and 

 Didinium, they possessing the protrusible snout of the latter combined with a wreath 

 of locomotive cirri, which, while discharging the more ordinary natatory functions, 

 are also endowed with saltatory properties. 



Mesodinium acarus, Stein. PL. XXXII. FIG. 40. 



Body subturbinate, the posterior portion globose, the anterior one 

 conical, the two regions separated from one another by a raised annular 

 border, from out of which are produced the circle of locomotive cirri ; con- 

 tractile vesicle spherical, posteriorly located. Length of body 1-800". 



HAB. Pond and marsh water. 



This species, as here figured, and obtained by the author from a number of 

 localities, is apparently identical with the type for which Stein first instituted the 

 generic title of Mesodinium. It may be readily distinguished from the two succeeding 

 salt-water forms by the raised border, bearing the locomotive cirri, which divides the 

 inflated posterior half from the conical anterior one. It has been frequently 



