ON THE BRITISH SPECIES OF GEISIA. 147 



Since some of the internodes which bore branches were 

 immature, and had not had time to develop more than one 

 branch, the figures would have been slightly different if the 

 growth of the colony had been complete. 



The symmetrical character of the branching noticed in other 

 species is also found in C. ramosa. Thus the branches 

 originating from an internode whose formula was (H + gr + rj) 

 developed altogether five internodes from which new branches 

 were given off; in two of these cases the branch was borne by 

 z^, in two more by z^, and in the last case by z^; and other cases 

 of the same kind may easily be found. 



The symmetry of the branching comes out with special 

 clearness in the case of some abnormalities, of which the 

 formula given on p. 145 is an example. Two consecutive inter- 

 nodes of the main stem represented in the formula give off 

 internodes whose formulae are identical. One of these gives off, 

 on its right side, a lateral branch consisting of a single long 

 internode bearing an ovicell, and the other gives off a precisely 

 similar branch on its left side. Both of these ovicells have the 

 same deformity, having developed a constriction at a particular 

 point near their upper end ; and it will further be noticed that 

 the symmetry extends, to some extent, to the branches given 

 off by the internodes which bear these ovicells. 



Fig. 13 represents an abnormal ovicell or zooecium of a type 

 found in more than one colony. The growing-point appears to 

 have started with the intention of developing an ovicell, and 

 then to have altered its original purpose, and to have developed 

 the incipient ovicell into an abnormal zooecium. This alteration 

 of purpose may have been due to the failure of the young 

 ovicell to develop the egg^ which is normally found in the 

 immature ovicell. 



The point which immediately concerns us at present is that 

 each of two consecutive internodes of the same stem of this 

 particular colony developed lateral branches, one on each side 

 of the stem, and that each of these lateral branches bore an 

 ovicell of this peculiar " suppressed " form. The same colony 

 * 'Proc. Cambridge Philosoph. Soc.,' vol. vii, p. 48. 



