11 
foot, the flapping wings as well as the more quiet hind part. The 
powerful, muscular mouth sucks the tissue of the host, the long, 
siender, mobile pedicel following every movement of the swimming 
animal, until the foot is retracted, when of course the parasite 
must release its hold. 
Systematical position. 
Kinetocodium danæ has evidently been modified in accordance 
with its special mode of living, its structure partly being some- 
what reduced, partly highly specialized. The modifications have not, 
however, gone so far as to efface the characteristics, necessary for 
determination of the systematical position of the species. Indeed, 
I have no doubt as to this point. 
The arrangement of the tentacles in a single verticil below a 
conical hypostome at once direct the attention towards the family 
Bougainvilliidæ. The lack of perisarc around the nutritive polyps 
might indicate a relation to the Hydractinia group; but in Kineto¬ 
codium this feature is undoubtedly a matter of adaptation, and the 
presence of perisarc around the gonophores distinctly separates it 
from the Hydractinia group. A comparison with the genus Perigo- 
nimus will show a series of similarities, which can leave no doubt 
of the relationship between the two genera. The long siender pol¬ 
yps of Kinetocodium may be regarded as Perigoniums- polyps with 
reduced perisarc and degenerate tentacles. In several species of 
Perigonimus the gonophores are placed directly on the stolons in 
the same way as in Kinetocodium ; they are surrounded by a perisarc 
and in certain species the perisarc remains unbroken until the gon- 
ophore has lost its connection with the mother polyp and closed 
its apical canal. Moreover the highly developed “mesenteries” in 
the gonophore of Kinetocodium demonstrate that the medusa, when 
liberated, belongs to the Tiaridæ, like the medusæ of Perigonimus. 
The early development of two opposite tentacular bulbs ahead of the 
next ones, points in the same direction. The “mesenteries” are, 
however, much farther developed in Kinetocodium than in gono¬ 
phores or young medusæ of Perigonimus. We may State, accord- 
ingly, that the present species belongs to the family Bougainvilliidæ 
and, within the latter, to the same group as Perigonimus ; but its 
difference from the latter, as well as from any other known genus, 
