1884.] Zoology. 197 
and the bell margin. The Oceania seemed not in the least incom- 
moded by the loss of the 
fourth and the reduction 
in size of a third radial 
tube, but moved with the 
same ease as if both were 
present and well develop- 
ed. ere is this inex- 
plicable relationship in 
the position of the two 
ought we to suppose the missing tube, if it had existed, to 
tube 3, h 
light on this question let us turn to the appendages of the bell 
margin, where we would naturally expect concomitant variations. 
Between g and 4 on the bell margin, corresponding to the angle 
a P b, there are seven otocysts and four well developed tentacles. 
tween sections æ and 4 of the margin, passing through ç, there 
are fourteen fully-formed otocysts and eight tentacles, or just 
“hell o Many as on the first mentioned portion of the rim. The 
bell margin shares with the remainder of the umbrella the trifid 
er indicated by the radial tubes. It seems to be, therefore, 
that the bell margin confirms a theory, which the radial tubes sug- 
Sest, that only three sectors exist in the umbrella, while the 
hi tla. unrepresented on the bell margin as in the body of the 
poen @ parasita—Among the hydroid Medusæ we find very 
ing ples of parasitic gonophores. One of the most interest- 
ese is the genus Mnestra, found parasitic on the abnor- 
mollusk, Phyllirhoé. The affinities of this Medusa have never 
been Satisfact 
orily made out, and nothing is yet known of its 
opment. 
aban’ existence of lateral appendages to the tentacles and the 
dei aa of Otocysts, leads me to place it somewhere near Zan- 
(Fi mmaria, The tentacles (Fig, 4 / are v 
'S. 6), and from thei 
ery stunte 
r tips there arises a cluster of lateral appen- 
