vi.] STONEWORTS. 45 



larger, the centre of the protoplasm becomes occupied by a 

 watery fluid, and its thick periphery, which remains applied 

 against the cell-wall, constitutes the wall of a sac, or pri- 

 mordial utricle, in which the nucleus is imbedded. In the 

 larger cells the primordial utricle is readily detached and 

 made to shrivel up into the middle of the cell by treatment 

 with strong alcohol. 



Numerous small green bodies chlorophyll grains are 

 imbedded in the outer, or superficial, part of the primordial 

 utricle. And they increase in number by division, as the 

 cell enlarges. These chlorophyll grains are composed of 

 protoplasmic matter, which frequently contains starch gra- 

 nules, and is impregnated with the green colouring sub- 

 stance. 



During life, the layer of the primordial utricle which 

 lies next to the watery contents of all the larger cells is in 

 a state of incessant rotatory motion, while the outermost 

 layer which contains the chlorophyll grains is quite still. 

 In the large cells, so long as the nucleus is discernible, it is 

 carried round with the rotating stream. 



The antheridium is a globular spheroidal body with a 

 thick wall, made up of eight pieces, which are united by 

 interlocking edges. The four pieces which make up the 

 hemisphere to which the stalk of the antheridium is at- 

 tached, are foursided, the other four are triangular. From 

 the centre of the inner, concave face of each piece a sort of 

 short process, the handle or manubrium^ projects into the 

 cavity of the hollow sphere. At the free end of the manu- 

 brium is a rounded body, the capitulum, which bears six 

 smaller, secondary capitula; and each secondary capitulum 

 gives attachment to four long filaments divided by trans- 

 verse partitions into a multitude (100 to 200) of small 

 chambers. Thus, there may be as many as 20,000 to 



