201 



in the same colony. Such a transformation of the cylindrical internodes is found 

 in most of the more developed colonies in one or several secondary branches, 

 and a growth in length and a division of the younger internodes take place at 

 the same time. 



We have already mentioned that in a colony at a certain stage of develop- 

 ment the outermost or sometimes the two outermost secondary branches on each 

 side are only composed of cylindrical internodes, and if we were to examine a 

 number of colonies at different stages of development we should find that these 

 whip-like secondary branches issue nearer the top stem-internode in the younger 

 colonies than in the older ones. Thus, if we were to designate the internode of 

 a main branch, issuing directly from the bifui-cate, distal stem-internode, no. 1, 

 the next no. 2 and so on, we should find that in colonies with 6 — 8 secondary 

 branches the whip-like secondary branches issue from internode 3—4, in colonies 

 with 9—12 from internode 4—6 and in colonies with 13 — 16 from internode 5 — 7. 

 This fact can only mean that all the zooecia in a number of outer secondary 

 branches arise by a transformation of cylindrical internodes. There is however 

 no certain rule for the time of the appearance of the fii-st whip-like secondary 

 branch, as in some colonies it may appear later than in others. The outermost 

 secondary branch on each side generally remains untransformed, and I have only 

 in very few cases foundU — S^of the proximal internodes transformed into zooecia 

 on one side of an older colony. A consequence of the conception that a number 

 of the older whip-like secondary branches are transformed into zooecia-bearing 

 ones and that new ones are formed outside these is, that the inner cylindrical 

 internodes of the main branches must at the same time be transformed into 

 bifurcate internodes. 



Whilst all the colonies of this species examined by me have arisen by gem- 

 mation from a branched stolon connected with other colonies, a fact explaining 

 the possibility that the development of a colony may begin with the formation 

 of a number of individuals (stem-internodes and branch-internodes) without or- 

 gans of nutrition, I have no doubt that a colony, proceeding directly from a 

 larva, must begin with the formation of a zooecium. Of this species I have been 

 able to examine numerous colonies obtained from a jointed calcareous alga 

 taken at Ajaccio by Dr. B0rgesen. 



Family Alysidiidae. 



The jointed colonies, springing from a stolonate network, consist of zooecia 

 and gonozooecia, the latter borne by stem-like kenozooecia. The zooecia, the distal 

 half of which has a depressed cryptocyst, are furnished with a simple opercular 



