372 



DISCOVERY REPORTS 



Annular zone. In most specimens the annular zone between the circular furrow 

 and the pedalia was distinctly visible; in a few, particularly flat ones, the annular zone 

 was covered by the overhanging lens and therefore apparently invisible, but it was 

 always present. In all high specimens with broad and deep coronal furrows, the annular 

 zone is very broad. Its presence or absence, as recently shown by Bigelow (1928), is of 

 no systematic importance, because it depends only on the degree of contraction of the 

 whole medusa. If covered by the central disc in flat specimens, it is easily made visible 

 by lifting the central disc. In several specimens I found fine radial furrows on the 

 annular zone corresponding to the furrows on the pedalia and the notches of the 

 central disc. 



Furrows on pedalia. In most specimens of the wyvillei type the furrows on the 

 pedalia are very distinctly visible, in a few the pedalia were smooth (e.g. St. 86). 

 This characteristic is thus not necessarily correlated with the deep notches of the 

 central disc. 



Gastro-vascular system (Figs. 4, 5). The present series oi AtoUa wyvillei diflFers 

 in respect of the gastro-vascular system from the descriptions given by previous authors 

 (Vanhoeff'en, 1903, for A. valdiviae; 

 Maas, 1904, for A. bairdi; and Bigelow, 

 1909, for wyvillei) by a much larger 

 amount of pigment in the canals and 

 pockets: the canals in the lappets reach 

 much farther distally than figured by 

 these authors, in whose figures they reach 

 only a little beyond the base of the 

 lappets. The tentacular pockets are very 

 much broader than the narrow rhopalar 

 canals; the pigment in the tentacular 

 pockets reaches right up to the border 

 of the lappets. The base of the tentacles 

 lies deeply enclosed in a sinus within the 

 tentacular pockets. The figures of Maas 



(1903, pi. iii, fig. 23 and 1904, pi. iv, fig. 34), which both show broad cathammal regions 

 on the base of the tentacles, agree less well than Vanhoefli'en's figure of the gastro-vascular 

 system of A. alexandri (1903, pi. vii, fig. 41), where the tentacular pockets surround the 

 base of the tentacles in a broad arch . Here, however, the tentacular pockets are represented 

 as being much less narrow than in the present specimens. It is very strange that in the 

 figures of these authors the canals entering the lappets are represented as being very 

 short. In the Discovery specimens they are always much longer and reach far into the 

 lappets, nearly to the end of the lappet pockets {cf. Vanhoefi^en, 1903, pi. vi, fig. 41 ; 

 Maas, 1897, pi. xi, fig. 2; 1904, pi. iv, figs. 33, 34; Bigelow, 1909, pi. viii). One 

 receives thus quite a different impression of the whole gastro-vascular system. 



Fig. 4. Atolla wyvillei, Haeckel, forma typica, mihi. 



Part of the gastro-vascular system of a young 



specimen. From St. 86, x 5. 



