f1 
from the sidewall of the hydrotheca; these two main-types of oper- 
cula are quite different and independent structures; and structures 
which, though resembling each other, are not homologous, cannot 
Jield any proof of a relationship. 
Cuspidella, Lafoéina and Stegopoma are undoubtedly nearly 
related forms; the operculum of Stegopoma is not very much different 
from that of Cuspidella and Lafoéina, and there is a great likeness 
in regard to the shape of the hydrotheca, though the hydrotheca of 
Stegopoma is usually provided with a well developed, pedicel. Broch 
(1912 b) has figured, however, some colonies of Stegopoma plicatile 
from the Kara Sea, on which the proximal part of some of the 
hydrothecæ is attached to the branch, and in the large colonies from 
West-Greenland the same is frequently the case (see figs. 1 and 2, 
p. 15). In reality, these hydrothecæ (the proximal part adnate to 
the branch, the distal part bent outwards) have a striking resem- 
blance to the hydrothecæ of Cuspidella procumbens Kramp. — It is 
true that the gonosomes have only little systematic value, but (with- 
Out being of the opinion that the fact mentioned in the following 
Fields any more proof of the relationship between the genera in 
hand) I may call attention to the fact, that the gonothecæ of all 
the three genera have the same shape as the corresponding hydro- 
thecæ, though they are partly somewhat larger. I think, that all 
8onothecæ originate from common hydrothecæ (as well as all blasto- 
Styles have originally borne hydrants), which have in most of the 
hydrøids transformed themselves according to their special function 
and developed into the very different forms, we know; .no wonder, 
therefore, that the gonothecæ cannot be used for classification!). In 
Cuspidella, Lafoéina and Stegopoma the gonothecæ have retained 
the shape of the hydrothecæ except, perhaps, in some species of 
Stegopoma (Levinsen (1913) mentions $%. geniculatum and pli- 
1) Compare the facts within the Haleciidæ, where in some species the 
blastostyle has retained its hydrants, and where a multiplicity of diffe- 
rent forms of gonothecæ are known, without any apparent connection 
with the relationship of the species. 
