TABLE OF REFERENCE LETTERS.

afr=adradial furrow.
afr´=furrow in Tripedalia that separates perradial from interrad. regions in lower half of bell. (In Charybdea the same furrow is directly continuous with afr.)
ax=axis of nerve.
c=concretion.
cc=canal underneath ivl, connecting the two adjacent marginal pockets.
ccl=circular canal.
ci=cilia.
cm=circular muscle.
co=cornea.
cp=capsule of lens.
cs=covering scale of niche.
csc=canal of sensory club.
ct=canal of tentacle.
ct´=beginning of canals of lateral tentacles in Tripedalia.
ec=ectoderm.
ece=ectoderm of exumbrella.
ecs=ectoderm of subumbrella.
ed=distal paired eye.
el=larger unpaired eye.
en=endoderm.
enc=endoderm of sensory club.
enf=tract of nerve fibres underlying endoderm.
enfl=endoderm of floor of stomach.
enp=endoderm of stomach pockets.
enr=endoderm of roof of stomach.
ens=endoderm of stomach.
ep=proximal paired eye.
es=smaller unpaired eye.
fc=funnel leading into canal of sensory clubs.
fp=fibre from subepithelial plexus of subumbrella.
fph=filaments of phacellus.
frn=frenulum.
ft=funnel-shaped depression in ectoderm axial to base of tentacle.
g=gelatine.
gc=ganglion cell.
ge=gelatine of exumbrella.
go=gastric ostium.
gs=gelatine of subumbrella.
hvl=horizontal vascular lamella.
i=interradius.
if=interradial funnel of bell cavity.
ifr=interradial furrow.
ivl=interradial vascular lamella.
l=lens.
lv=lip of valve.
m=bell margin.
mc=mucous cell.
mep=mesogonial pocket.
mo=mouth.
mp=marginal pocket.
mp´=smaller marginal pockets, in Tripedalia.
mst=muscle of stock of sensory club.
mt=muscle at base of tentacle.
n=nerve.
nc=network cells, in sensory club.
nf=nerve fibres.
nm=nematocyst.
nst=nerve of stalk of sensory club.
osn=outline of sensory niche.
p=perradius.
pe=pedalium.
ph=phacellus.
pr=proboscis.
r=reproductive organ.
rc=remains of concretion.
rcl=radial canal.
rg=radial ganglion.
rm=radial muscle.
rn=radial nerve.
rns=root of nerve of sensory club.
rs?=remains of stalk (?) of sensory organ.
rt=retina.
s=stomach.
sc=bell cavity.
scl=sensory club.
scn=supporting cell of nerve.
se=sensory epithelium.
sh=shrinkage space.
sl=stalk of lens.
sla=supporting lamella.
sn=sensory niche.
so=sensory organ in proboscis of Tripedalia.
sp=stomach pocket.
sph=stalk of phacellus.
ss=stalk of sensory organ, in proboscis.
st=stalk of sensory club.
su=suspensorium.
sub=subumbrella.
tl=lateral tentacle.
tm=median tentacle.
v=velarium.
va=vacuole.
vb=vitreous body.
vc=velar canals.
ve=edge of velarium.
vfs=visual fibres, according to Schewiakoff.
vg=valve of gastric ostium.
vl=vascular lamella.
vlc=vascular lamella connecting vls with vlm.
vlm=vascular lamella of margin.
vls=vascular lamella of sensory niche.
vlst=vascular lamella of sensory niche at base of stalk.
wc=wandering cells.
w-x-y-z=successive levels of Figs. 40-43 on Fig. 5.