STRUCTURE OF SPERMARY 



21 



ones have each its lower angle truncated by the insertion of 

 the stalk, so that they are actually four-sided. 



Each shield (Fig. 48, A and B, s/i) is a single concavo- 

 convex cell having on its inner surface numerous orange- 

 coloured chromatophores : owing to the disposition of these 

 on the inner surface only, the spermary appears to have a 



B 



FIG. 48. A, diagrammatic vertical section of the spermary of Nitella, 

 showing the stalk (stk), four of the eight shields (s/i), each bearing on 

 its inner face a handle (/in), to which is attached a head-cell (/id) : each 

 head-cell bears six secondary head-cells (hd 1 ), to each of which four 

 spermatic filaments (sp. f, ) are attached. 



B, one of the proximal shields (s/i), with handle (/in), head-cell (/id), 

 secondary head-cells (/id'), and spermatic filaments (sp. f.). 



C, a single sperm. 



D 1 , D 2 , D 3 , three stages in the development of the spermary. 

 (c after Howes.) 



colourless transparent outer layer like an orange inclosed 

 in a close-fitting glass case. 



Attached to the middle of the inner surface of each shield 

 is a cylindrical cell, the handle (/in), which extends towards 

 the centre of the spermary, and, like the shield itself, con- 

 tains orange chromatophores. Each of the eight handles 

 bears a colourless head-cell (1id'\ to which six secondary head- 



