12 
catile, but as will be seen from the following, p. 16, the gonotheca 
of St. plicatile has just the shape of the hydrotheca with a similar 
operculum, though it is much larger). 
To the other main-group of “ Campanulinidæ" belong, I think, 
the genera Calycella , Tetrapoma , Thyroscypus and, perhaps, Lovenella 
(according to H ar ti au b Lovenella produces a medusa very much 
like Phialidium , the medusa of Campanularia Johnstoni). 
I am not able to see any connection between these two main- 
groups of genera. 
As to the genus Campanulina thorough investigations are 
necessary before anything definitely can be said about its systematic 
position; the operculum in this genus seems to be of a similar 
shape as that of Cuspidella, but according to Hartlaub Campanulina 
acuminata Alder has a “true” operculum like that of Lovenella ; 
this shows, that the usual conception of the shape of the opercula 
within this genus is not beyond question, before new investigations 
have been carried out, especially on the development of the 
operculum of several species of Campanulina in order to obtain 
certain information, whether the operculum takes origin from the 
roof or from the sidewalljof the hydrotheca. The medusæ render an 
argument against a relationship between Campanulina and Cuspidella. 
The medusa of Cuspidella belongs to the genus Laodice, while some 
species of Campanulina are known to produce medusæ belonging 
to the family Eucopidæ ; if Hartlaub is right, that the medusa of 
Lovenella belongs also to the Eucopidæ , it seems possible, that 
Campanulina and Lovenella , and possibly Tetrapoma, Thyroscyphus 
and Calycella are related forms. But Hartlaub has not only shown, 
that Campanulina acuminata has an operculum like that of Lovenella , 
but moreover, that its medusa is Aequorea Forskalea; if this be 
correct, it increases very much the difficulties of the systematic 
problems within the u Campanulinidæ ". 
It has frequently been mentioned, that a common classification 
of the hydroids and the medusæ is very difficult and meets with 
several contradictions. Some authors give up all attempts at con- 
