2 
of the parasite turned out to be a Polype with medusæ-buds in 
various stages of development. Thus the question evidently was of 
some colony of Hydroids; but the stem soon turned out to be, not 
aå part of a Hydroid, but of a Parasitic Copepod, belonging to the 
family of Lernæidæ. Without destroying the beautiful specimen 
given by Mr, Blegvad, I reached this conclusion. from a thorough 
search for parasites in the rich collection of Scopelini from the 
Atlantic, which our Museum had obtained from the steamer "Thor". 
More than two thousand specimens of Scopelini were examined for 
this purpose; I succeeded in finding 6 other specimens of the 
"combined parasite”; some of these had egg-strings — or remnants 
of egg-strings — still adhering, and thus did not leave any doubt 
about the nature of the '"stem”. The new material did not contain 
any specimen so richly developed as the first one, but on the other 
hand it yielded developmental stages both of the Hydroid and of 
the Parasitic Copepod. Especially the latter seem to me of some 
value as a supplement to what has been known hitherto of the 
metamorphosis of some other Lernæidæ (Lernæa, PennellaJ. 
My material, further, shows that the association of the Hydroid 
with the Parasitic Copepod is not a necessary” one, in so far 
that the parasitic Crustacean may be found without the Hydroid; 
on the other hand, I never found the Hydroid without the Copepod, 
though the fact is not unknown that some Hydroids grow directly 
on the body of fishes (2; 7a, b; 13; 20a; 8, 9). 
That the association is not an accidental one seems to be 
proved by the fact that a proportionally large number of the Para- 
sitic Copepod carry the Hydroid. 22 specimens of the Copepod 
in its final form, inserted into the body of the fish, were found; 
but of these 8 are very young and the part protruding outside the 
fish is so small, that it could not be expected beforehand, that 
any Hydroid should attach itself upon it; of the remaining 14 large 
and adult specimens just half the number bear the Hydroid. 
The Copepod, consequently also the association, appears to be 
bound to a single species of host, Scopelus glacialis Rhdt.; and 
