186 DEScniPTiON OF XFolygastrica. 



it "woTold be rightly placed in Peridinea. Length l-1440th to 

 1 -840th. 



Astasia (?) vwidis. Body extensible, and of an ovate-oblong form, 

 distended a little at the middle ; tail very short and pointed ; green. 

 Found amongst Conferva. Length l-1200th to l-900th. 



A. nivalis. — Form oval, extremities rounded, rarely pear-shaped, 

 colour deep reddish-brown, motion rapid. Found with Protococcus 

 nehulostcs in snow (Switzerland). (P. 12, Group 526.) Length 

 l-1500th. 



M. Vogt in his account of the Astasia nivalis, describes it as 

 invested with a carapace (lorica), open only at the anterior extremity. 

 This opening is furnished with numerous small cilia, and here, doubt- 

 less, the mouth is situated, the indication of which is given by an 

 orange-coloured tint, which is clearer than that of the rest of the 

 animal. " The presence of the lorica together with the cilia, are 

 characters which do not allow this animalcule to be placed with 

 Astasia, as Shuttleworth has done : on the contrary, it ought to be 

 placed in the family Peridinia (Ehr.) ; or otherwise be regarded as the 

 type of a new genus, distingtiished by the absence of a grove in the 

 lorica, and by the stiff hairs of Peridinia being replaced by soft cilia." 

 (On the Animalcules of the Red Snow. — Bibliotheque TJnivers de 

 Geneve.) 



A. aeus. — Body hyaline, of a long fusiform figure, acute at each 

 end, filament the length of the body. Length 1 -650th. Berlin, 



Dujardin's genus Astasia, is defined as colourless, obtuse, or 

 rounded posteriorly, whilst those described by Ehrenberg, are mostly 

 green or red, and provided with a longer or shorter caudal pro- 

 longation. 



The following species are from Dujardiu. 



A. contorta — Body colourless, semi-transparent, containing pale 

 yellow granules, cylindroid, enlarged at the middle, obtuse at each 

 end, and marked with oblique striae, giving rise to a twisted appear- 

 ance. Length 1 -450th. Found in sea water. 



A. injlata. — Body semi-transparent, diaphanous, contractile, ovoid, 

 obliquely, but regularly plaited or striated. Length 1 -560th. In 

 sea water. 



A. limpida. — ^Body diaphanous, smooth, very variable fusiform, 

 more or less obtuse at each end, cleft anteriorly, and often obliquely 



