14 EDWARD T. BROWNE. 
small opposite perradial tentacles at an early stage of development, with filaments 
just appearing. Four interradial marginal bulbs and eight adradial bulbs, smaller 
than the interradial. 
Size.—Umbrella about 4 mm. in width and height. 
The presence of two long opposite perradial tentacles in the early stage indicates 
that this Medusa begins its free-swimming career with only two tentacles. The genus 
Catablema is very closely related to the genus Tiara. It is known that Tvara pileata 
is liberated from a hydroid belonging to the genus Perigonimus, and that on liberation 
the Medusa has only two opposite perradial tentacles. It is very likely that Catablema 
is also liberated from a Perigonimus-like hydroid. The early stages of Catablema 
weldoni were taken in January and June, and the adults during April and May. 
The ‘Discovery’ collection contains nine specimens of this new species, which 
can be easily distinguished from the others of the genus by the tentacles possessing 
filaments with nematocysts, and by the length of the lateral diverticula of the radial 
canals. The specimens all came from under the ice in McMurdo Sound. There are 
two early stages with four tentacles, and two intermediate stages with 9 and 12 
tentacles. The others are adults with 16 tentacles. Only two specimens are in good 
condition. 
The ‘Southern Cross’ collection possesses ten specimens, all of which are in a 
very bad and rotten condition. They are solely recognisable by the structure of the 
tentacles and by the lateral diverticula of the radial canals. These specimens, 
however, were useful, for some are larger in size and possess more tentacles than those 
in the other collection. They were all taken at Cape Adare, at the surface and near 
the beach, on 10th May, 1899. Temperature of the sea, 27° F. 
As the stomach is large, its attachment to the roof of the umbrellar cavity is 
strengthened by “mesenteries.” These so-called mesenteries are formed by outgrowths 
of the stomach alonz a portion of the radial canals, and consequently the canals leave 
the stomach not at the top, but laterally. In Catablema weldoni, the outgrowths are 
very short, extending just over the top of the umbrellar cavity, and unless specially 
searched for are likely to be overlooked. Prof. Haeckel attached importance to the 
presence or absence of mesenteries in his classification of the Tiaridz, and included 
them in the character of the genera. They are not true mesenteries, such as 
Ptychogastria polaris possesses, but simply outgrowths of the stomach, and their 
extension along the canals depends greatly upon the size and weight of the stomach. 
The gonads (Plate L, fig. 5) are arranged in eight straight, adradial, longitudinal 
rows, which extend along the whole length of the stomach. Each row is composed 
of many small transverse folds, which bear the generative cells. The arrangement 
of the gonads in straight rows is only seen in those specimens which have the stomach 
properly expanded. Two specimens have their stomachs contracted back, and the 
gonads are curved and thrown back against the top of the umbrellar cavity. 
In Catablema campanula, Haeckel, the diverticula of the radial canals are short 
