GENERAL REMARKS. 36/ 



the opercle, and a central mass, separated from the wall by 

 green parenchyma: the structure of this mass varies, above it 

 is greenish, and towards the middle there is as it were, a 

 stricture, the lower part disappears subsequently by absorp- 

 tion. 



The changes henceforth consist in an enlargement of the 

 columella and a corresponding reduction in the size of the ca- 

 vitv as well as of the central mass under the stalk of the 

 columella, in the separation of the tissue of the outer wall at 

 the base of the opercle, in the formation or appearance of a 

 membrane round the columella, which still remains attached 

 to the inside of the opercle. This is 6rst indicated by an 

 opaque line. 



The inner membrane and columella go on enlarging, and 

 finally occupy almost all the cavity of the theca, the opercle 

 becomes more distinct, the annulus appears. Intervening be- 

 tween the apex of the columella, and the inside of the oper- 

 cle appears a production from the inner membrane — the outer 

 peristome and afterwards the inner, and including the corres- 

 ponding changes in the sporula, the theca may be said to be 

 perfectly developed. 



The teeth of the outer peristome, are binary only at apex, 

 the outer is just marked out, but not coloured when the ring 

 of the opercle is first tinged with orange, the inner is barely 

 traceable at this time. 



The last thing organised is the inner peristome, it is just 

 perceptible when all the rest of the parts except the sporules 

 are perfectly formed. 



It is probably the presence of the peristome, that causes 

 the separation of the head of the columella from the inside of 

 the opercle, it is at once obvious that in all peristomed 

 mosses its points of adhesion, so strong originally up to a late 

 date, must be much reduced, as Hymenostomum, Lyellia, etc. 



The whole process is singular, first we have the greatest 

 development downwards, then downwards and upwards, then 

 upwards alone. 



