MEDUSAS OF THE HAWAIIAN ISLANDS. 
1137 
specimens, and they come from identical, or almost identical, localities, there is reason to suppose that 
they represent merely stages of growth of Periphylla dodecabostrychci. 
Figures 5 and 6, plate ii, show the shape of the bell in the smallest and largest medusa, respectively. 
It may be seen that when the medusa is small the bell is higher than it is wide, whereas in the large 
medusa the bell is wider than it is high in the proportion of about 10 to 7. 
All of the specimens obtained by the Albatross are quite deeply pigmented with brownish-purple, 
the pigment extending into the entodermal pouches of the lappets, and being so dense in the zones of 
the circular and the radial muscle fibers that it is difficult to see the form and position of the gonads by 
looking through from the outside of the bell. 
Attention should be called to the fact that it seems hazardous to attempt to separate the various 
species or races of Periphylla, on the ground of relative height and width of the bell, for the form of 
the bell appears to change with age, becoming flatter and relatively wider as the medusa grows larger. 
Both Maas (1904) and Vanhoffen (1902) agree that in P. hyacinthina the bell is relatively high and 
the pigmentation so dense that the gonads can not be seen by looking through the walls of the bell; 
whereas in P. dodecabostrycha the bell is flatter, its apex is blunter, and the pigmentation is lighter, so 
that the gonads may be seen more or less clearly by looking through the bell walls from the outside. 
However, in 1892 (taf. i, fig. 1), Vanhoffen gives a figure of “P. hyacinthina” from life showing the 
gonads clearly visible through the hyaline walls of the pedal zone. 
Similarly in P. regina, Maas (1897, taf. x) shows the bell only faintly pigmented, whereas 
Vanhoffen (1902), in his report upon the Scyphomedusse of the Valdivia expedition, shows it quite 
densely pigmented. Vanhoffen (1902) concludes that the species described by Fewkes, Haeckel, etc., 
can be reduced to three, namely, P. hyacinthina Steenstrup (1837), P. dodecabostrycha Brandt (1838), 
and P. regina Haeckel (1880). 
The species are separated mainly upon color differences, shape of bell, and size at the time of the 
development of the gonads. It should be borne in mind, however, that these are characters which 
are most apt to be individually a locally variable in medusae. For example, the varieties and local 
races of Cyanea or Obelia along the Atlantic coast of the United States differ onefrom.the other in just 
such characters; yet any attempt to separate them specifically leads to confusion, for there are inter- 
mediate forms that prevent such classification. The case may be somewhat similar with Periphylla, 
and it is possible that all of the so-called species may in the end prove to be local races of one and 
the same form. However this may be it has been demonstrated by the Plankton, Valdivia , and Siboga 
expeditions that the Periphyllidse are truly deep-sea medusae, living at or near the bottom, and only 
upon rare occasions coming to the surface. 
It seems unnecessary to redescribe Periphylla dodecabostrycha after the excellent studies and figures 
of Vanhoffen and Maas, but for the sake of clearness we will enumerate some of the characteristic 
features of its anatomy. 
Specific characters: Bell higher than wide in young, wider than high in well-grown medusae. Four 
interradial marginal sense organs, 12 solid tentacles, and 16 spatula-like marginal lappets. Exumbrella 
with a deep annular furrow, and below this a zone of 16 thick gelatinous pedalia, one for each mar- 
ginal sense organ and tentacle. The pedalia are separated one from another by deep longitudinal 
clefts which extend from the annular furrow downward through the mid region of each lappet. 
Thus the pedalia alternate in position with the lappets. Each sense organ contains a protruding sac 
of otoliths, and a mass of entodermal pigment. (See Maas, 1903, taf. ii, fig. 15. ) 
There is a zone of well-developed circular muscles in the subumbrella above the bases of the ten- 
tacles. This zone is divided into 16 parts by 16 selvages. Each selvage extends down the middle of 
a lappet so that the reflected halves of each pair of adjacent lappets are connected by circular muscle 
fibers. There are 8 longitudinal areas of radial muscles in the subumbreila above the zone of circular 
muscles. Four of these are radial and 4 interradial. Eight V-shaped gonads alternate in position with 
the 8 strands of longitudinal muscles, the open ends of the V’s being uppermost. The central stomach 
is wide, and is continued into the gastro- vascular space of the bell in 4 elongate radial clefts, the edges 
of which are lined with gastric cirri. A partial septum extends down the middle line of each lappet, 
and the gastro-vascular space forms a canal around this septum. The medusa is more or less deeply 
pigmented with purple-brown, which is especially well developed in the entoderm, but is sufficiently 
translucent to allow one to see the gonads showing faintly through the bell walls. The annular furrow 
and the clefts between the pedalia of the exumbrella exhibit brown ectodermal pigment. The ten- 
tacles are white, while the gelatinous substance of the bell is hyaline. 
