11 
from the sidewall of the hydrotheca; tbese two main-types of oper- 
cula are quite different and independent structures; and structures 
which, though resembling eacb other, are not homologous, cannot 
yield any proof of a relationsbip. 
Cuspidellct , Lafoeina and Stegopoma are undoubtedly nearly 
related forms; tbe operculum of Stegopoma is not very much different 
from tbat of Cuspidella and Lafoeina, and tbere is a great likeness 
in regard to tbe sbape of tbe hydrotheca, thougb the hydrotheca of 
Stegopoma is usually provided witli 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 
hvdrothecæ 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 faet mentioned in the following 
yields any more proof of the relationship between the genera in 
hånd) I may call attention to the faet, 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 
gonothecæ originate from common hydrothecæ (as well as all blasto- 
styles have originally borne hydrants), which have in most of the 
hydroids transformed themselves according to their special funetion 
and developed into the verv different forms, we know; no wonder, 
therefore, that the gonothecæ cannot be used for classification 1 ). In 
Cuspidella , Lafoeina and Stegopoma the gonothecæ have retained 
the shape of the hydrothecæ except, perhaps, in some species of 
Stegopoma (Le vin sen (1913) mentions St. geniculatum and pli- 
x ) Compare the facts within the Hcdeciidæ, where in some species the 
blastostyle has retained its hydrants, and where a multiplicity of diffe¬ 
rent forms of gonothecæ are known, witliout any apparent connection 
with the relationship of the species. 
