308 XXII. REPRODUCTION OF 



striae, come together only in the middle of the cell. They lie 

 close to the inner wall of the shield; whence it came that in 

 examining the entire antheridium a dark red centre appeared to 

 be surrounded by a clear sheath. 



If we examine now a young but fully-formed antheridium, we 

 can determine that the shields fit together by the indentations of 

 their margins, and that eight shields, to wit, four above and four 

 below, are combined in the wall. The four upper have the form 

 of triangles, the four lower are quadrangular, because an angle 

 of each of these latter is cut off, leaving a short side by which it 

 joins on to the stalk of the antheridium. 



A complete insight into the structure of the antheridium can 

 However only be obtained by means of sections. To obtain these 

 is not so difficult as might at first sight appear. A branch 

 covered with sexual organs is placed between the fingers, the 

 sexual organs turned inwards, and it is then halved longitudi- 

 nally with a sharp razor. As a rule this suffices, but we may 

 try to further divide one of the halves, so as to obtain a median 

 longitudinal section. If this has been effected, we obtain the 

 structure as shown in the annexed figure 112, A, a. The inser- 

 tion of the antheridium (a) in the branch is clear. The stalk of 

 the antheridium (p), with its wall lined with orange-red chromato- 

 phores, projects right into the interior of the antheridium. From 

 the centres of the shields spring the manubria (m) ; the capitula 

 seated thereon impinge upon one another and upon the stalk-cell. 

 From the secondary capitula we can see pro- 

 ceeding the threads of mother-cells of the 

 spermatozoids. 



Now let us again take the preparation with 

 the crushed antheridium, which we had laid on 

 one side. If this had been quite ripe, the sper- 

 matozoids will now, after the lapse of an hour 

 or two, have commenced to free themselves from 

 the threads. They emerge from their mother- 

 FIG. 113.-A sper- cel1 b Y a lateral opening, showing brightly 



matozoidof Gtora/ra- through a swelling substance which has been 



gilw nxed with osmic . 



acid vapour. The dar- squeezed out from it. They are corkscrew-like 



threads < Fi g; 113 )- with four complete turns. 



At a little distance from their anterior, some- 

 what tapered, end they bear two very long cilia, longer than the 

 entire body of the spermatozoid, and readily recognisable after 



