236 WILSON. [VoL. II. 
two endoderm sacs grow up from the ceelenteron in the shorter 
axis, and the cesophagus is then surrounded by four sacs. The 
sacs are the intermesenteric chambers, and their partition walls 
form the mesenteries. Gétte concludes that in this develop- 
ment there is no stage which corresponds to the hypothetical 
hydropolyp ancestor. The young Scyphostoma itself, which 
has hitherto been regarded as a hydropolyp with tzenioles, is in 
reality an Anthozoan with four complete mesenteries ; and the 
development previous to the Scyphostoma does not pass through 
a hydroid stage, but, on the contrary, jumps directly from a 
hollow planula to the larva provided with two (later four) endo- 
dermal sacs. This larva is called the Scyphula, and from Kow- 
alevsky’s account of the development of Cerzanthus (4), Godtte 
believes it to be common to both the Scyphomedusze and An- 
thozoa, and consequently an ancestral form. In Cerzanthus 
according to the abstract given by Hoffman and Schwalbe of 
Kowalevsky’s paper, the cesophageal invagination does push 
down the endoderm along two opposite meridians; but though 
the abstract is not definite on this point, the implication is that 
the meridians are those of future mesenteries. If this is so, 
Cerianthus agrees essentially with Manicina, and not with 
Aurelia. 
The ancestral Scyphula form was derived, according to Gotte, 
directly from the hollow planula, the invagination of the cesoph- 
agus necessitating the simultaneous formation of endoderm 
sacs. The infra-cesophageal mesenteric ridges, from this point of 
view, are not of any phylogenetic importance, and have nothing 
to do with the endoderm ridges of Tubularian or Siphonophore 
polyps; they have come into existence merely as the after-result 
of the formation of endodermal sacs. This theory contains in 
itself an obvious difficulty: the sudden and direct transforma- 
tion of such a simple form as the planula into such a complex 
form as the Scyphula. What could have caused this complex 
group of changes, Gétte does not suggest. But aside from this 
objection it seems clear that the development of Aurelia is a 
highly modified form of the development of Manzcina, and the 
manner in which this peculiarly symmetrical modification was 
brought about is suggested by the variations shown in Figs. 
30-33. 
If Fig. 30 is compared with the woodcut Fig. 1, it is seen that 
