CCENOBlEyE ,295 



oospheres, are mature, the movement of the cilia begins to set the entire 

 antherid in motion ; but it shortly breaks up, and the separate anthero- 

 zoids are seen in rapid motion within their gelatinous envelope, which 

 they ultimately break through, and then move about rapidly in all 

 directions within the cavity of the parent-colony. They assemble in 

 large numbers round the oogones, and some of them finally penetrate 

 through the gelatinous membranes of these organs, and coalesce with 

 the oospheres. The number of sexual reproductive colonies within a 

 parent-colony varies greatly ; Cohn has observed five or six male and 

 about forty female. The impregnated oosphere now becomes an oosperm 

 by the development of a cell-wall of cellulose, which is at first single 

 and smooth, but becomes subsequently differentiated into three distinct 

 layers, of which the two inner ones are smooth, while the outermost 

 becomes ultimately covered with conical or warty elevations, giving it 

 on section a stellate appearance. The chlorophyll of the oosperms 

 gradually disappears, and is replaced by an orange-red pigment dissolved 

 in oil, giving a red tinge to the entire organism as seen by the naked 

 eye. Soon after the maturity of the oosperms, the parent-colony breaks 

 up, and the peripheral swarm-cells escape from the combination and 

 swim about freely in the water ; their further history has not been traced. 

 The orange-yellow oosperms sink to the bottom, and there hibernate as 

 hypnosperms. Their contents are said to break up into eight Volvox- 

 colonies, which ultimately escape by the rupture of the outer and absorp- 

 tion of the inner coats of the oosperm, and swarm about in the water. 



In Eudorina Ehrb. the coenobe is a hollow ellipsoid body, consisting: 

 of usually i6 or 32 cells enclosed in a gelatinous envelope, each pro- 

 vided with two long cilia which protrude fhrough canals in the envelope,, 

 and a red pigment-spot. Daughter-colonies are formed non-sexually 

 within the parent-colony by repeated bipartition of its cells, the cells of 

 the daughter-colony being arranged in a disc. The male and female: 

 reproductive bodies are formed in special daughter-colonies which may- 

 be termed antherids and oogones respectively; the oospheres, contained! 

 in the oogones are each provided with two cilia, and are therefore true 

 zoospheres ; the antherozoids, which closely resemble those ' of Volvox, 

 swarm round the oogones until their cilia become entangled in those of 

 the zoospheres ; they then force their way into the gelatinous envelope 

 of the oospheres, and finally coalesce with them. 



Volvox and Eudorina are regarded by Ehrenberg and Stein as, 

 belonging to the Flagellate Infusoria. 



Under the name of Scyamina, Van Tieghem (Bull. Soc. Bot. France,. 

 1880, p. 200) describes a singular blackish organism found on the surface 

 of ponds, which he regards as a genus of Volvocineae destitute of" 

 chlorophyll. 



