186 DESCRIPTION OF [Poli/<jastrica. 



or four, are generally attached together in a line, as shewn 

 vcifig. 106. Ixijig. 105, two are seen, with two young ones 

 growing between them. Size of each globe l-l720th. 

 Found amongst conferva. 



Genus XLVIII. Sphaebastrum. The round- star Ani- 

 malcules are characterized by their members being free, 

 having a simple univalved smooth and turgid lorica, and 

 by forming, during self-division, different shaped groups. 

 A slight change of place or locomotion has been observed, 

 but little or nothing of their organization is known, 

 though Bory and Turpin have stated the existence of 

 male seminal glands in S. quadrijuga. 



171. Sphaerastrum pictum. The globular Sphaeras- 

 trum has oval green corpuscles, passing into spherical 

 clusters, of the form of a mulberry. Size of berry 

 l-480th; of single member l-1920th. Found with 

 Micrasterias. 



172. Sphaerastrum quadrijugum. The four-rayed 

 Sphaerastrum has oblong green corpuscles, four being 

 united into cubical masses, perforated at the middle. Size 

 of berry l-570th; of single member 1 -1200th. Found 

 with the former species. 



Genus XLIX. Xanthidium. The double-bar Animal- 

 cules. — The animalcules of this genus are characterized by 

 being free (devoid of pedicle or stalk) and having a simple 

 univalved lorica, of a globular form, surrounded with 

 spines. They are found either single, in pairs, or groups 

 of four. Ehrenberg thinks they may sometimes be de- 

 veloped in the form of a chain. The lorica is clear, like 

 glass or parchment, covered with simple or branched 

 bristles, like spines. No aperture has been discovered 



