THE ANTHOCEROTES 



149 



(2) has also studied this species, and his results agree entirely 

 with those of the writer. 



The thallus much resembles a small Anthoceros, and sec- 

 tions through it show that in its growth and the development 

 and structure of the sexual organs there is close correspondence. 

 The thallus contains very large lacunae, which are formed in 

 pretty regular acropetal order, and vertical sections show these 

 large cavities increasing regularly in size as they recede from 

 the apex. Similar but less regular lacunae occur in A. fusifor- 

 mis. The antheridia arise as in Anthoceros, endogenously. 

 The youngest stage found is shown in Fig. 80, A. Here evi- 



FxG. 80. — Notothylas orbicularis. Development of the antheridium. D, cross-section, 

 the others longitudinal sections; E, nearly ripe antheridium, X300, the other fig- 

 ures X600; (^, A, the primary antheridial cells. 



dently the young antheridia (<?) have been formed by the longi- 

 tudinal division of a single hypodermal cell, whose sister epider- 

 mal cell has divided again by a transverse wall to form the outer 

 wall of the antheridial cavity (Figs. A, B). The commonest 

 number of antheridia formed is four. 



Less regularity is found in the next divisions than in Antho- 

 ceros, although in the main they are the same. This is observ- 

 able both in longitudinal and cross-sections (see Fig. 80, D). 



