102 



to strengthen the resisting power of the otherwise slightly calcilied stem. Along 

 the middle of the frontal surface of each segment we find an exceedingly nar- 

 row membranous frontal area, which even in its distal part is furnished with 

 parietal muscles (figs. Im — In), which Kirkpatrick has also found in B. 

 (Stirparia) Haddoni. New colonies arise from the stems of the older, taking their 

 origin between two contiguous segments, and the youngest, which have a very 

 small number of zooecia, possess only a single stem-segment, which in time 

 increases in length and seems to be formed by a constriction of the proximal 

 part of the ancestrula (figs. 1 c, 1 d, 1 f). After the ancestrula follow two still 

 solitary zocecia, after which the first bifurcation commences. The older colonies, 

 with from 3 — 17 joints, have only one solitary zocecium, which according to the 

 age of the colonj' sometimes has altogether 2 — 3 spines, and sometimes none at 

 all, while the distal wall, as in the segments is connected with two calcified 

 bands which are fused together in the proximal part of the zocEcium into a ring. 

 A larger or smaller number of the older zocecia according to their age show 

 a similar transformation, and a comparison between the youngest and oldest 

 colonies leaves no doubt about the fact, that the solitary zooecia in the proximal 

 portion of the colony are in time transformed to segments, while the proximal 

 segment arises from a constriction of the proximal part of the ancestrula. I cannot 

 determine with certainty how the other segments are formed, but as new colonies 

 can arise between two segments, it seems reasonable to suppose, that new seg- 

 ments can also be formed between two older ones, and the fact that the seg- 

 ments may have a very different length favours this supposition. Nevertheless, I 

 have nowhere found them so short that I could consider them as just beginning. 



The radical fibres, which in the older parts of the stems issue in numbers 

 from uniporous rosette-plales in the areas between the two strong, calcified bands, 

 are simple calcified fibres, which partly cover the trunks, partly project freely 

 from these. In some places they are pear-shaped, swollen in a part of their 

 course and contain a strongly refractive, shining mass, while such swellings at 

 other places project freely and thereby assume a great likeness to the gonothecse 

 in the Hgdrozoa. As far as the phj^siological importance of these swellings is 

 concerned, I would put forward the supposition that they serve for the accumu- 

 lation of reserve materials. Waters' has found quite similar formations in JBii- 

 gula {Stirparia) glabra Hincks. 



The colonies are frequently compound, and the small colonies have the form 

 of stalked caliculate tufts, the branches of which show 6 bifurcations in the 



' 111, p. 20, fig. 1. 



