28 FOSSIL MEDUS.. 
1-3 of Pl. 1), but in the great majority it could only have been very narrow 
and deep. Whether it was more than a simple tube, uniting the radial 
exumbrella canals and the oral canals, is doubtful. In such specimens as 
those represented by figs. 4, 4a, 4b, 8, 8a of Pl. I, there is little space for 
any central divisions of the intestinal canal. Such a space is represented, 
however, in text figs. 6 and 7, as it is improbable that a simple intestinal 
canal existed in such forms and the divided canal in others, like text fig. 4. 
In the fossils the central axis or disk is usually distorted by compres- 
sion and penetrated through and through by fine annelid borings. The 
presence of the central stomach is sug- 
gested by the frequent collapse of the 
central disk immediately above its nor- 
mal place (PI. I, fig. 2); over forty 
individuals before me show this with 
marked distinctness. The central 
stomach is clearly indicated in fig. 4 of 
Pl. If], where the radial intestine of the 
exumbrella lobes passes into it. This 
is also shown in the transverse sections 
(Pl. IV, figs. 7, 8, 9) and in vertical 
vertical section through the umbrella lobes. sections (Pl. IV, figs. 10, 11). The 
a, exumbrella lobes, with radial canals; d, section of 
umbrella lobes; 0, oral arms, with interior canal; /, buceal stomach is indicated by fig. Sb 
undifferentiated central axis that in the living animal 
was probably the seat of the genitalia, etc., as in some of Pl. ie 
recent forms (see text fig. 3, p. 11); g, position of the i c . 
central stomach; h, position of the buccal stomach; i, Coronal intestine. By this term Haeckel 
points extending downward in the stomach that suggest 
a former opening to a central mouth; k, axial canals, includes the entire peripheral gastro- 
corresponding to the pillar canals of text fig. 3, p. 11. vascular system of medusze which sur- 
rounds the central or principal intestine and communicates with it by the 
gastral opening. He considers that in the Acraspeda the typical and origi- 
nal arrangement was four wide perradial pouches, which begin at the cir- 
cumference of the central stomach and run in the subumbrella toward the 
umbrella margin, where they are united by a coronal canal. 
This typical quadripartite pouch corona of the Seyphomedusz has been developed 
from the simple gastral space of their ancestors, the Seyphopolyps, by the four inter- 
radial teniola of the latter being laid together and fused at four points (of equal 
height), cr in four streaks, by their upper dorsal parts and lower ventral parts. In 
this way four small interradial nodes or narrow ridges are originated, which form 
incomplete septa between four wide perradial pouches.! 
‘Haeckel, loc. cit., p. Ixxxix, par. 126. 
