ON THE BRITISH SPEOIES OP OEISIA. 125 



taking up colouring matters ; slightly later a young polypide 

 bud is seen below the diaphragm, which is then absorbedj the 

 zooecium growing out (in C. ramosa) into a long tubular 

 portion, at the end of which is the aperture.^ In C. ramosa 

 the free portions of regenerated zooecia are sometimes con- 

 siderably longer than the normal length of the tubular portion. 

 In one case the regenerated portion, which was completely free 

 from the branch, was "69 mm. long. 



It is well known that new stems are given off from various 

 parts of the rootlets.^ These 'rootlets are usually developed 

 from the backs or sides of the zooecia, especially of those near 

 the base of the colony. But in cases where regeneration is 

 actively taking place the tip of a branch may grow out into a 

 rootlet, or a rootlet may take the place formerly occupied by a 

 zooecium, usually one of the terminal zooecia of an internode in 

 this case.^ The rootlet thus formed may grow for a considerable 

 distance, and finally produce a new stem as a lateral branch ; 

 or the new stem may be the actual prolongation of the rootlet, 

 which, after a longer or shorter course, assumes the characters 

 of a stem. In other cases a new growing-point is formed 

 from an old joint at the point where a lateral branch or an axial 

 internode has previously been lost ; or it may be formed from 

 the apex of an internode in which the fracture has taken place 

 across the middle of the internode, instead of at an axial joint. 

 The result of this is that it is very common to observe an old 

 brown stem from which start new internodes (lateral or axial), 

 which are shown, by reason of the perfectly white appearance 

 of their ectocyst, to have been formed at a much later period 

 than the brown part of the stem. In one or two cases a 

 growing-point had started from the proximal side of a broken 

 joint, and had then given rise to a stem which grew in a direc- 

 tion directly opposite to that of the internode from which it 

 was developed. These cases are somewhat analogous to the 



' This is the process which was observed by Smitt in C. geniculata. 

 = Cf. Smitt, "Krit. Port.," i, 'Ofvers.,' &c., 186S, p. 122. 

 ' These statements refer, for the most part, to C. eburnea and to C. 

 ramosa. 



VOL. V, PART II. 13 



