356 



P. Kramp. 



^ 



main branch and continue tlieir growth out along the other branch; 

 a mutual exchange of tubes thus occurs, which produces a close and 

 intimate connection between the two, intercrossing branches (text- 

 figure 1); of this I have seen a great many examples in Lafoëa 

 friiticosa and Toichoponni oblùiiiiim. 



A young branch, which as yet only consists of one tube, may 

 at its end fasten itself to another branch, grow a little way along 

 this and twine round it like a tendril (PI. XX, figs. 1,2); the tendril- 

 like nature of these branches seems in some cases to be determined 

 beforehand, as they bear no hydranths over a long distance before 

 they reach the point of attachment (figs. 2, 4); but I have often seen 



cases also, wiiere ordinary hydrotheca- 

 bearing branches have fastened themselves 

 to a neighbouring branch (e. g. fig. 1). Two 

 young branches (with or without hydranths) 

 which meet, may unite and form a double 

 bridge between their respective main 

 branches (text-figure 2); from both of these 

 /3 branches new tubes may grow out along 

 the bridge and make this thicker and more 

 solid. I have seen many bridges like this 

 on vigorous, dense colonies of Lafoëa frii- 

 ticosa. Plate XX fig. 8 represents a very strongly developed bridge 

 on an old colony. A single tendril may naturally also form the 

 foundation for a polysiphonic bridge, in that new tubes may grow 

 out on it from both sides. 



Coalescences and bridges of all thicknesses are found in Lafoëa 

 friiticosa, of which species the material of the Expedition contains a 

 great many large colonies, and partly in Toichoponni obliqmim and 

 Lafoëa grandis. 



I have also seen the transformation of the ends of branches to 

 creeping stolons in the genera Haleciiim and Sertnlarella. In Haleciiim 

 with compound stem I have only observed two such cases; they 

 are both figured on Plate XXI. Fig. 1 show^s a branch of H. miirica- 

 tum, which has come into touch with a piece of shell, has fastened 

 itself on this and grown out a stolon on each side. Fig. 2 is a 

 branch of H. labrosnin ; from a hydiotheca there has grown, not a 

 new hydrotheca, l)ut a rather long, somewhat wrinkled thread which 

 has attached itself to a piece of shell and sent out ramified stolons. 

 In Haleciiim textiim, whose stems and branches are monosiphonic, 

 branches and pseudohydrocauli^ are often stolonized and help to 

 ^ Series of hydrothecae; see Schydlowsky, 1901 (51). 



Text-fig. 2. 



