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were, the fellow of the cup placed upon the primary cell (a). This 

 cup, marked (d) in the figure, arises in a dilated ampulla, like those in 

 the branches (to which I shall allude afterwards), on the same side of 

 the axis as the cell a". This ampulla or dilated portion, which must 

 be considered in the light of a distinct cell or compartment of 

 the axis, analogous to the other compartments in the radical disk and 

 tubes before described, gives off laterally the stem of the cup, and is 

 continued upwards iuto the cell b", which, from its superior and in- 

 ternal angle, gives off a tubular prolongation, which passes on the 

 posterior aspect of the branch till it reaches nearly the level of 

 the upper border of the next pair of cells, where it expands either 

 iuto two branches supporting cups, or into one such branch, and a 

 wider one which expands into the lowermost or solitary cell of the 

 other branch of the first fork, or the branch which forms the fellow to 

 the one, the lowest cell of which was derived from the primary cell 

 b, as before described. The remaining cell (c) also arises in a distinct 

 compartment, like the former, and in this case, the arrangement, 

 though apparently different, is actually the same. The new element 

 of the polypidom, from whence the cell (c) is derived, originates in a 

 narrow tube, also seen on the posterior aspect of the branch on the op- 

 posite side of the axis to the ampulla of the first cup, from which it 

 is separated by a partition, and ascending on the posterior aspect and 

 between the first regular pair of cells b and b", when it reaches their 

 upper border, it divides into or gives off two lateral branches (sup- 

 porting the cups e, e) and is continued upwards into the cell (c), from 

 the upper and internal border of which a tubular prolongation arises, 

 which follows the same course as the similar processes from the other 

 cells. 1 have been thus prolix in describing the mode of origin and 

 continuation of the cells, as 1 think the structure I am describing so 

 imperfectly is extremely curious and deserving of close investigation. 

 But the arrangement will be better understood by the inspection of 

 the figures or of specimens than from any verbal description. 



It may be sufficient to say, that corresponding to each fork, two 

 fresh series of polypi ferous cells are, as it were, intercalated into the 

 polypidom, in a manner precisely similar to the two last described. 

 I would also particularly draw attention to one point, which may 

 perhaps, hereafter, serve to throw considerable light upon the real 

 nature of the cups, and consequently upon the true nature and rela- 

 tions of the analogous organs in the other Bryozoa. It will be 

 observed that each separate series of cells is connected at its origin 

 with one or more cups, according to the number of pairs of cells on 



