VOLVOCINEJS, 71 



able, a single colony may on the second day develop 16, on the third 

 256, on the fourth 4,090, and at the end of the week 268,435,456 other 

 organisms like itself. 



It has been supposed that some of the cells become detached from the 

 mature coenobium and pass into a resting condition, but this has not been 

 positively demonstrated, so that figuration is the only mode of repro- 

 duction at present known. 



A fuller abstract of this paper by Cohn (from " Nora Acta," Vol. 

 XXIV., p. IGity is given in Fritchard's Infusoria (p. 153). 



Plate XXVII. fig. 1. Goniuni pectoral?. a, b, c, families in different 

 positions X 400 ; d, e, the same, rather more highly magnified ; /, family 

 before division; g, family of 16 cells divided into 16 daughter families ; 

 d to g after Stein. 



GENUS 43. STEPHANOSPHJERA. Cohn. (1852.) 



Coenobium throughout its whole life rotating and moving, 

 composed of 8 green cells, bearing two vibratile cilia, disposed 

 at equal distances around a circle, enclosed in a common 

 colourless hyaline, globose vesicle. 



Propagation, both by macrogonidia arising from the eight- 

 fold division of the green cells, bearing two cilia, with a lateral 

 red spot, congregated in families of eight ; and by niicrogonidia, 

 very much smaller, produced by multiplied division, at first re- 

 volving within the common vesicle by the action of four cilia, 

 afterwards free, escaping singly. 



Stephanosphaera pluvialis. Cohn Bedrvigia i.,p. 11. 



Cells globose, elliptic or fusiform, often at each extremity 

 spreading out in mucous rays. 



SIZE. Ccenobium -026--052 mm. Cells -006--012 mm. 

 diani . 



Rabh. Alg. Eur. iii. 100. Currey in Micr. Journ., 1858, vi. 

 p. 131, t. 6, f. 1-27. Cohn Zeitschr. fur Wiss. Zool., 1852, 

 iv. p. 77. Archer Micr. Journ., 1865, p. 116. Pritchard Inf. 

 p. 529, t. 19, f. 38-58. 



In hollows of rocks, and in pools after rain. 



StepJianospJifsra was first observed in 1850 in Germany, and since in 

 many places, including the British Isles. 



It consists of a hyaline globe, containing eight green primordial cells, 

 arranged in a circle in its equator. The globe rotates upon an axis per- 

 pendicular to the plane in which the primordial cells are arranged, and 

 moves actively in space by the aid of cilia, two of which proceed from 

 each of the primordial cells, and pierce the hyaline envelope. The 

 primordial cells divide first into two, then four, and lastly into eight 

 portions ; these portions separate from each other in a tangential direc- 

 tion, thus forming a disc round which a cellular membrane is developed. 

 Two cilia are produced upon each segment, and thus eventually eight 

 young individuals are formed, which ultimately escape by fissure of the 



