Cotylorhiza and Rhizostoma. 179 
internal circlets of large exumbral urticating pads, and by the 
rudiments of the four primary gastral filaments, which, in our 
larvee, have already attained a very considerable size. The 
buccal tube is already characterized by the strength of its 
wall and the thickness of its jelly, and it is still destitute of 
the four arms, so that the Ephyra of Cotylorhiza would have 
to be described as “‘ cannostomous”’ in Hickel’s sense. 
During the gradual growth the umbrellar disk of the larva 
constantly acquires a greater extension in comparison with 
the eight lobes; in other words, the distal extension of the 
interradii advances more rapidly than that of the radii. In 
Ephyre which only slightly exceed the diameter of 2 millim. 
the proportion between the length of the lobe-stems and the 
radius of the umbrellar disk already appears distinctly altered 
in favour of the latter. While in the youngest Ephyre it 
represented 13:1, the semidiameter of the disk has already 
attained the length of the eight lobe-stems. We may regard 
this larval form as asecond Ephyra-stage, because on the oral 
part of the buccal tube new structures have made their appear- 
ance which seem to be of very great importance in the deve- 
lopment of rhizostomism, and in combination with the strength 
of the wall already indicated, pave the way towards the very 
divergent structure of the buccal arms. Thus on the free 
border of the buccal tube short tentacles have grown forth, 
even before there could be any reference to the presence of 
buccal tentacles. ‘The number of filaments is now doubled. 
In the vascular apparatus no essential alteration is yet per- 
ceptible, although lateral diverticula already appear on the 
radial canals, tending towards a union with the intermediate 
canals to form the annular canal. 
The larvee of about 24-3 millim. diameter show an essen- 
tially altered form, short pointed velar lobes making their 
appearance in the interradi, which already considerably ex- 
ceed half the length of the radii. ‘These stages already possess 
a closed annular canal, for the formation of which the diver- 
ticula of the radial vessels have united with the intermediate 
canals ; and also four well-marked buccal arms beset with ten- 
tacles. ‘They represent the floresca-stage. Moreover the 
buccal arms, independently of the tentacular fringe on their 
elongated distal margin, already show a complication pre- 
aring the way for the future pairs of arms, in the shape of 
two lateral folds diverging in a fork distally. The number of 
filaments has advanced to 3-4 in each radius, and the 
occupation of the entoderm by vegetable cells is denser 
in comparison with the younger larve. In connexion with 
the appearance of the marginal corpuscles the cord-like con- 
