66 HOFMKISTKR, ON 



five cells which is borne by an elongated cylindrical 

 stem consisting of a single row of cells (PI. XI, fig. 1, 40). 



The cells of the latter continue to divide frequently by 

 septa parallel to those already present. The central cell 

 of the spherical head which it supports multiplies actively 

 in all three directions by repeated bisections (PI. IX, fig. 

 31 ; PI. XI, figs. 2, 41), whilst the cells of its outer layer 

 divide only by septa at right angles to the outer surface, and 

 much less frequently than the central cell. The anthe- 

 ridium is now a spherical mass of small cells filled with 

 mucilage, surrounded by a single layer of tabular cells con- 

 taining chlorophyll (PL XI, "fig. 3). In each of those 

 smaller cells a spermatozoon is formed inside an ellipsoidal 

 or spherical vesicle (PI. VII, fig. 6; PI. XI, fig. 42). 

 When the antheridium is ripe, the cells of its outer layer* 

 separate from one another (PI. VI, fig. 37 ; PI. XI, fig. 42) ; 

 the vesicles containing the spermatozoa, which have become 

 free by the dissolution of the walls of the cellules containing 

 them, escape in the form of a mucilaginous mass. They 

 disperse themselves under water, and commence a rotating 

 motion. The wall of the vesicle bursts, the enclosed 

 spermatozoon escapes either wholly or partially (PI. XI, 

 fig. 42), and moves about in the water, keeping up a per- 

 petual rotation round the axis of the spiral which it pre- 

 sents (PI. VII, fig. 12; PI. VIII, fig. 3). 



In the antheridia of those species in which division by 

 alternately inclined septa commences even in the earliest 

 primary cell of the antheridium, the essential parts, i. e., the 

 mother-cells of the first degree of the spermatozoa and 

 their covering layer, are developed in a precisely similar 

 manner. A long series of cells of the second degree fail to 

 multiply, so that a cylindrical double row of cells (long in 

 Madotheca, short in Fossombronia) represents the second 

 stage of development of the antheridium. The free end of 

 this cylinder swells up to a clavate shape ; and in the two 

 youngest cells the divisions now ensue which lead to the 

 formation of the central cell and its covering layer. 



* In some species (e. g., Fosssombrouia pusilla) the granules of chlorophyll in 

 these cells have by this time become yellow, as is the case in Anthoceros, and 

 in the mosses. 



