ment); but how, I am not able to decide. That they as true para¬ 
sites should feed directly on the tissues of the fish is possible, 
but seems less probable; neither in Hydrichthys nor in Nudi- 
clava are the hydrorhizæ sunk into the skin, and the latter 
appears not to be affected by tkeir presence (the same holds good 
for the Scopeli carryin g Ichthyocodiurn); more likely they are mess- 
mates or commensals, feeding on leavings from the meals of the 
fish or perhaps on the excrement of the latter. I may add that 
I found no contents at all in the gastric cavity of the polypes of 
Ichthyocodiurn which I have cut in sections. 
Explanation of the plates. 
List of reference letters. 
a = anus. 
a 1 = antennule. 
a 2 = antenna. 
f = furcal appendage. 
* y — genital segment. 
I = chitinous thickening. 
m = manubrium of medusa-bud. 
md — inandibular palp. 
me = medusa-bud. 
mp 1 = maxilliped of first pair. 
mp 2 = maxilliped of second pair. 
mx = maxilla. 
o = genital opening. 
p = polype. 
p 1 —p 3 == first to third abdominal (thoracic) foot. 
pr — lateral outgrowth from cephalothorax. 
r = marginal tentacle of medusa-bud. 
si = sipho. 
Plate I. 
Fig. 1: Scopelus glacialis Rhdt. with the combined parasite, composed of 
the Sarcotretes scopeli (without egg-strings) and the Ichthyocodiurn 
sarcotretis. X c. 2. 
— 2: enlarged view of part of the same specimen of Sarcotretes (the 
stalk and proximal part of the swollen external portion) with part 
of the Hydroid-colony. me 1 = large medusa-bud having lost one 
of its marginal tentacles. 
