279 
found both in a nuraber of species belonging to the latter group 
and in Odontotheca macrocarpa Bale. 
A species, which presents a still greater variation, is Thujaria 
heteromorpha Allm. 1 ), which according to the author possesSes two 
diffeient forms of hydrothecae, some in which the margin is nearlv 
circular and even directed away from the supporting internode, 
and others 2 ) in which it is “directed towards the internode, and 
has its apocauline margin produced into a short, slightly incurved 
tooth. While the former are placed in the proximal part of the 
branches, the internodes of which carry many hydrothecae, the 
latter are seated in the distal part, and here each internode bears 
a single pair of hydrothecae. A further difference is that the 
hydrothecae of every pair are in some internodes connate to one 
another, but in others separate. 
A lim an expresses his doubt as to the correct reference of 
this species to Thujaria in the following way: “Amid systematic 
characters pointing in so many different directions, it would seem 
difficult to decide on the true generic position of our Hydroid,” 
and I shall hereto remark that we shall only be able to solve this 
question when we get information about the structure and position 
of the operculum, but otherwise the shape and position of the 
aperture in the two different' forms of hydrothecae leave little doubt 
that the species must belong to the genus Diphasia. 
b 4, p. 147. 
“) According to the figures given by Allman the last named hydrothecae 
have quite the same form as those found in Thujaria pharmacopola 
Allm. (5, p. 66), but as pointed out by Billard (10, p. 1857) the 
latter species is identical with Diphasia alata Hincks, and the 
hydrothecae of this species have not the slightest likeness with All¬ 
man s picture, their abcauline margin being broadly rounded and 
not at all acuminate. Therefore I am not quite sure, whether the 
corresponding hydrothecae of Th. heteromorpha are correctly figured. 
In the same paper Billard points ’out that Thecocladium flabellum 
is a Sertularella, that Thujaria pectinata is identical with Th. arti- 
culata Pall. and Th. vineta with Sertularella quadridens Bale. 
Having examined myself fragments of the original speeimens of the 
three first named species I can confirm as to them the correctness 
of Billard’s observation. 
