182 Scientific Proceedings, Royal Dublin Society. 
In the allied forms, Depastrella, Tessera, and Tesserantha, 
Haeckel figures ridges running along the umbrella, and dividing 
it and the stalk or crest into four regions. No such ridges are to 
be seen in Depastrum cyathiforme. In his description of this 
animal, Allman states that the stalk is ringed regularly. We 
have seen rings on the stalk when it is not stretched to its full 
length, but they are not constant, are sometimes incomplete, 
and invariably disappear when the animal is erected to its full 
height. 
In adult forms the umbrella usually exhibits a somewhat 
quadrilocular form, being bulged out by the the large bundles of 
generative organs which are arranged in four V-shaped dark 
masses, and may be distinctly seen through the more pellucid 
body-wall. 
In a few specimens we found existing a hexagonal, not an 
octagonal, arrangement of the parts; one such specimen had 108 
tentacles in twelve groups of nine each, approximately equal. 
The tentacles, when the animal was not quite expanded, appeared 
not to be arranged in groups, but to form three continous rows. 
Sections of this specimen showed that it possessed six mesenteries, 
six gastro-genital pockets, and six radial chambers. We found 
that the arrangement of mesenteries and chambers in normal 
specimens, as revealed by sections, agreed with that described 
by H. James-Clark. 
Sections cut across a very young specimen demonstrated the 
absence of the radial chambers in the earlier stages of growth. 
Longitudinal sections show that the animal possesses a circular 
muscle, ectodermal in origin. The mesogloea is thrown into a 
number of folds which project out into the ectoderm, and on 
which the muscles cells are arranged. The muscle is well defined 
and by no means diffuse. It is situated outside the tentacles, and 
its presence will account for the appearance of the contracted 
animal. 
As the result of the careful examination of numerous specimens, 
continued over an extended period of time, we are of opinion that 
the animals described by Sars, Allman, and Gosse, must all be rele- 
gated to one and the same species as that which we have found. 
We believe that the different points of distinction attributed by 
Sars to Lucernaria cyathiformis (Fauna Litt. Norveg. [1846] p. 26, 
