DEVELOPMENT OF THE GONADS 



215 



narrow canal which places the distal end of the ovum in free 

 communication with the surrounding water. 



We saw how the various parts of the fully formed plant- 

 nodal, and internodal cells, leaves, and rhizoids were all 

 formed by the modification of similar cells produced in the 

 apical bud. It is interesting to find that the same is true of 

 the diverse parts of the reproductive organs. 



The spermary arises as a single stalked globular cell which 



sp.c 



ov- 



FIG. 49. A, vertical section of the ovary of Nitella, showing the 

 stalk (stk}, small node (nd) from which spring the five spirally-twisted 

 cells (sp. c), each ending in one of the two-celled sections of the crown 

 (cr). The ovum contains starch grains, and is represented as trans- 

 parent, the spiral cells being seen through it. 



B 1 , surface view, and B 2 , section of a very young ovaiy : B 3 , later 

 stage in vertical section : B 4 , still later stage, surface view, with the 

 ovum seen through the transparent spiral cells. Letters as in A, except 

 x, small cells formed by division from the base of the ovum. (B 2 -B 4 

 after Sachs.) 



becomes divided into eight octants (Fig. 48 D 1 ). Each of 

 these then divides tangentially (i.e. parallel to the surface 

 of the sphere) into two cells (D 2 ), the inner of which divides 

 again (o 1 ) so that each octant is now composed of three cells. 

 Of these the outermost forms the shield, the middle, the 

 handle, and the inner the head-cell : from the latter the 

 secondary head-cells and spermatic filaments are produced 



