20 BULLETIN OF THE 



as occurring on Gonopodaria and P. Belgica, budding does occur to a 

 slight extent on Arthropodaria, and still raore profusely on Urnatella. 

 There is one genus, however, Barentsia (Vigilius, '84^, p. 86), which buds 

 sparsely and has an imsegmented stalk. Here, howevei", as in Urnatella 

 (Plate VI. Fig. 58) and Arthropodaria (T), there is a septum between the 

 branches and the main stalk. 



Finally, in all Pedicelliuidse which have been studied carefully there 

 is a septum between the stalk and calyx. 



One may bring these scattered facts of distribution of the septum into 

 some sort of unity by saying that in the Pedicellinidse every calyx and 

 every lateral branch (where such exists) is partly cut off from communi- 

 cation with the interior of the mother stalk by septa. This is effected 

 by the production of these organs at the place of junction of the calyx 

 and the lateral buds to the stalk, and in some cases also by the partial 

 division of the stalk itself into compartments by septa. The transverse 

 septa must have either a morphological or a physiological significance. 

 They might be regarded as a part of the wall of zooecia, equivalent to 

 the zooecia of Paludicella, and therefore to be morphologically equiva- 

 lent to the septa of Paludicella. On this hypothesis each segment of 

 the stalk of Urnatella would be an (incomplete) individual. The idea of 

 the individuality of the segments would seem to be sustained by the fact 

 that each gives rise to similar buds, and that apparently any segment 

 has the capacity of regenerating the lost calyx, or end of the primary 

 stalk. On the other hand, dissepiments might be regarded as structures 

 which had grown across the originally unsegmented stem to fulfil some 

 need of the organism. Comparative anatomical studies seem to me to 

 favor the second view. In Loxosoma, and in most marine Pedicellinidee, 

 we find a stalk without dissepiments. In other forms dissepiments 

 are few and variable in number, in still others they ai'e constant in 

 occurrence, and from the segments arise buds. Finally, in Urnatella, 

 the segments are separated by the dissepiments, each becomes more in- 

 dividualized, and has the capacity of giving rise to buds having the same 

 arrangement. The differentiation of the separate segments has gone so 

 far that one can hardly see in the stalk of Urnatella, resembling a string 

 of beads, the assumed smooth cylindrical stem of its Pedicellina-like 

 ancestors. 



If we seek for an explanation of the dissepiments, I think it is to be 

 found in the protection of the stock against the influx of water and de- 

 stroying organisms at the time of the loss of calyx or lateral branches, 

 which would make regeneration impossible. This is the same hypothe- 



