File:A naturalist's rambles on the Devonshire coast (Page 87) (5980713049).jpg

THE MARGINAL CAPSULES. 87
circle : they do not appear to be organically connected
with the tentacles. Each of these organs consists of
a transparent globe, not enveloped in the substance
of the disk, but so free, as to appear barely in contact
with it (see fig. 2) : it contains a smaller globule or
lens, of high refractive power, placed excentrically
towards the outer side. The inexperienced naturalist
on first seeing these organs would unhesitatingly
pronounce them eyes. They are, however, considered
as rudimentary organs of hearing; the crystalline
globule or otoliths being capable of vibration within
its vesicle. Their exact counterparts are found in
most of the small Medusae, a tribe of animals, which
this tiny zoophytic embryo represents in its whole
form and structure.
The disk is endowed with an energetic power of
contraction, by -which the margin is diminished,
exactly like that of a Medusa in swimming ; and tlie
tentacles liave also the power of individual motion,
though in general this is languid, their rapid flapping
being the effect of the contraction and expansion of
the disk just mentioned, producing a quick involution
and evolution of the margin, and carrying the tentacles
with it. Occasionally, however, all the tentacles are
strongly brought together at their tips, as at fig. 5, with
a twitching grasping action, like that of fingers, which
is certainly independent of the disk, and may be co7i-
nected with the capture of prey.
Several months afterwards, having obtained some
populous colonies of this species attached to al^ce, I
selected some, to examine afresh their embryology.