II 



MUSCINE^—HEPA TIC^— MARCH ANTI ALES 



51 



sented as empty. The antheridium becomes sunk in the thallus 

 precisely as in Riccia. The sperm cells are nearly cubical and 

 the spermatozoid is formed in the usual way. The free 

 spermatozoid (Fig. 16, D) shows about one and a half com- 

 plete turns of a spiral. The cilia are very long, and the vesicle 

 usually plainly evident. 



According to Ikeno (4), in Marchantia polymorpha the 

 final division, resulting in the pair of spermatids, is unaccom- 

 panied by a division wall, and this seems also to be the case in 



Fig. 16.— Fimbriaria Californica. A. Longitudinal section of a fully-developed male 

 receptacle, X8; B, longitudinal section of a nearly ripe antheridium, Xioo; C, 

 young sperm cells, X6oo; D, spermatozoids, X1200. 



Fimbriaria. In the earlier divisions of the sperm-cells, each 

 cell shows two centrosomes (Fig. 17, i), and Ikeno does not 

 recognise any difference between these and the so-called 

 ''blepharoplast" of Webber and other recent students of sperma- 

 togenesis, who look upon the blepharoplast as a different organ 

 from the centrosome. After the final division, each spermatid 

 is provided with a single centrosome (blepharoplast), from 

 which, later, the cilia arise. 



