12 
is so great that it must be the representative of a new genus, 
Kinetocodium. — The great variation in the number of rudimentary 
tentacles, which may even be quite absent, indicates that the spec¬ 
ies is still in a degenerating condition. 
Remarks on some related species. 
The two species of Hydrichthys as well as Ichthyocodium sarco- 
tretis Jungersen all live in connection (directly or indirectly) with 
pelagical fishes and are greatly modified in accordance to their 
peculiar modes of living. The modifications go partly in the same 
directions as in Kinetocodium, but are much more highly accomp- 
lished, so much so, that a discussion of their systematical position 
can only be founded on the gonosomes, whereas the trophosomes 
give no idea whatever of the affinities of the species. 
In his description of Hydrichthys mirus, Fewkes (1888) dis- 
cusses the question of the systematical position of this interesting 
form. His considerations are, however, a series of more or less 
hazardous analogizings. It is not worth while to deal with his com- 
parisons between Hydrichthys and Tubularia (pp. 229—230) or Po- 
lypodium (p. 232); nor do I apply much importance to his indic- 
ations of a relationship to Velella (p. 231). With regard to the 
medusa of Hydrichthys, Fewkes States as follows (p. 228): “Shortly 
after its detachment, the medusa with two tentacles resembles a 
young Stomotoca" and (p. 229): “The medusa with two opposite 
tentacles was raised into one with four, passing out of the stage 
resembling Stomotoca into one like Sarsia ”. — Stechow (1909) 
in his description of Hydrichtella epigorgia (a hydroid epizoic on a 
Gorgonid) compares the enerusting hydrorhiza and the naked nutri- 
tive polyps, devoid of tentacles, of Hydrichtella with the corres- 
ponding structures in Hydrichthys. These features are, however, in 
both species matters of adaptation and have no systematic value 
at all. Owing to the capitate tentacles of the defensive polyps he 
refers Hydrichtella to the Corynidæ, and he adds (p. 33): "... dazu 
kommt die offenbar sehr nahe Verwandtschaft mit Hydrichthys. Dort 
weisen die Medusen, hier die Tentakel der Wehrpolypen mit gros¬ 
ser Bestimmtheit auf die Corvniden, und so schliesse ich auch diese 
Form den Coryniden an”. This view is entirely wrong. The only 
points of likeness between Hydrichtella and Hydricthys are due to 
