22 
The polypes are completely devoid of tentacles; their mouth 
is ofteu expanded into trumpet-shape. When the mouth is expanded 
the oral entoderm is everted to form the disc or trumpet. Im- 
mediately below the disc is seen a narrow, feebly thickened ring, 
consisting of cylindrical ectoderm-cells somewhat higher than those 
of the rest of the body. Inside this ring the entodermal circular 
muscle-fibres are more strongly developed than in the remaining 
part of the body, these fibres evidently acting as a sphincter. 
When the mouth is closed, the ring-cells bound the mouth-pore. 
The body is cylindrical or claviform, 
sometimes goblet-shaped; the total 
length ca. 1 —1,5 mm., the diameter 
from 0,048 to 0,176 mm. In the 
outer ectoderm of the membrane 
are numerous fairly large nemato- 
cysts, but I have not been able to 
detect any nematocysts whatever in 
the ectoderm of the polypes. In 
the most developed colony (PI. I, 
Fig. 1) the largest polypes are found 
on the ventral side of the parasitic 
copepod turned towards the fish 
(therefore not shown in the figure). 
A proportionally great number of 
these large polypes (1,5 mm. or somewhat more in length) do not carry 
any medusæ-buds; but as a few of them bear a single large bud, 
some others a few small buds at their base, no definite demarcation 
between sterile and fertile polypes can be drawn, as already stated. 
Towards the margins of tbe colony almost all polypes are fertile. 
The distal part of those polypes which carry a great number of 
medusæ-buds — up to ca. 20 — is generally very siender and easily 
overlooked while more or less concealed among their buds (cfr. 
textfigure 5); but polypes with only a few or only small buds may 
have quite the same shape as those without anv buds at all. 
Fig. 5. Ichthyocodium sarcotretis. 
Polype carrying medusæ-buds. p: 
polype; m: manubrium of medusa- 
bud; r : marginal tentacle, the 
greater part of which is bent up 
inside the beil and indicated as 
seen through the latter. 
