100 DISCOPHOR^. Part III. 



which the lower floor becomes here connected with the uj^per floor along the 

 crooked lines, PI. V*. Fig. 23 k. We have thus sixteen defined areas of concentric 

 folds, eight of Avhich are narrow and eight broad, and thirty-two bundles of radiating 

 folds, sixteen of which are longer, bordering on the narrow pouches, and sixteen 

 shorter, bordering on the bi'oad or tentacular pouches, though at first it may appear 

 as if there were only sixteen such radiating bunches. A closer examination (PI. 

 IV. Fiff. 2) shows plainly how the triangular prolongation of each narrow area of 

 concentric folds is connected with two bundles {b) of longer radiating folds, and 

 each wider area of concentric folds is equally connected with two bundles (e) of 

 short radiating folds. The dividing line between these longer and shorter bundles 

 corresponds to the crooked lines ; and as the gelatinous ridges, which form these 

 lines, separate the narrow from the broad pouches, it is plain that the long bundles 

 are folds of the lower floor of the narrow pouches, and the short bundles folds of 

 the lower floor of the broad pouches. 



In describing the folds of the lower floor, I have thus far only alluded to their 

 most prominent aspect, as seen from the lower surface of the disk ; but it is 

 evident that, unless their structure be more complicated than it seems to be at 

 first sight, it would not be possible for such prominent ruflles, placed so close to 

 each other, to retain their relative jDOsition in a curtain stretched over the extensive 

 surface which they cover, unless they were held together by immovable fastenings. 

 This is secured in two ways. In the first place, they are soldered to the upper 

 floor along the crooked lines; in the second place, they are not simple folds, but 

 the lower floor consists of two layers folding in ojDposite directions, in such a 

 manner that the longitudinal folds of one layer are held together by the transverse 

 folds of the other layer, and vice versa ; while, at the intersections, the surfaces 

 circumscribed are pressed against each other in the form of little sei'ial sacks, as 

 may best be understood b}^ a comparison of figures 12 and 13, of PI. V^, Fig. 12 

 representing the concentric folds, / and d', as seen from the outer surface, and 

 Fig. 13, the same folds on a somewhat larger scale, in a transverse section. Fig. 

 3 b and c represents the same arrangement, on a smaller scale, for the radiating 

 folds. PI. IV. Fig. 7, represents the concentric folds from the inner surface turned 

 towards the main cavity, where the radiating folds of the inner layer, Avhich hold 

 them together, are more strongly marked than the concentric folds themselves, 

 which are most prominent on the outer surface. Secured in this way, this double 

 system of concentric and radiating folds is not only held together, but forms 

 innumerable serial pouches, alternately gaping inwardly and outwardly ; and as 

 Cyanea advances in age, each pouch becomes more complicated by the deepening 

 of the pouches and the further folding of their walls, eventually giving them the 

 aspect of rows of comb-like sacs. It has already been stated, that the folded part 



