Messrs. Hancock and Embleton on the Anatomy of Kolis. 193 
motion of the water they curl up their foot and fall to the 
bottom. 
The oral tentacles, which are kept in perpetual action, seem 
to possess the sense of touch in an exquisite degree ; so much so 
that we are led to conclude, that from this circumstance, and 
from their anterior position, they ought to be regarded as special 
organs of touch. . 
_ Taste, if present, most probably resides in the lining mem- 
brane of the buccal cavity, particularly in the folds at the back 
of the tongue (1st paper, Pl. I. fig.8 4) and the cheek-mass, ef, 
and perhaps also in the laminz at the commencement of the 
cesophagus. 
When describing the third pair of nerves, we stated that we 
considered the dersal tentacles to which these nerves pass to be 
distributed, as the olfactory organs, and for this opinion we now 
proceed to adduce reasons which appear to be sufficient. 
That these tentacles are special and very important organs, a 
consideration of the internal anatomical arrangement of their 
nervous element and of the peculiarities of their external form, 
peculiarities susceptible of great variety, would seem to leave very 
‘little doubt in the unprejudiced mind. 
First of all a large nerve, Pl. V. fig.3, among the largest in 
the body, comes off from the front of the median cerebral gan- 
glion ; and secondly, this nerve, or more properly speaking, trac- 
tus, has superadded to it at the base of the tentacle a well- 
defined ganglionic swelling, ¢, of a size exactly proportioned to 
the extent of complexity in the external form of the tentacle. 
Thus in E. papillosa, in which the tentacle is smooth and in its 
simplest form, the ganglion is considerably less than in EL. coro- 
nata, Pi. VI. fig. 6, and E. Drummondi, in both of which the 
tentacle has a surface of a far more complicated kind, being ren- 
dered much more extensive by the addition of numerous broad, 
circular lamine ; the ganglion being in these two species, as be- 
fore noticed, upwards of one-third the size of the lateral supra- 
cesophageal ganglion itself, Pl. VI. fig. 1 e, and Pl. V. fig. 2 e. 
If further evidence be required to illustrate the importance 
and special nature of these organs, we may go from the genus 
Holis to the other members of the family Kolzdida, as for in- 
stance to Humenis marmorata, in which we find the laminz so 
closely set as to conceal the whole shaft of the tentacle, and 
moreover there exists a sheath at the base of the tentacle into 
which it can be retracted at the will of the animal. A sheath 
also exists in Doio, Pl. VI. fig. 7, into which the organ, though 
simple in form, is completely retractile. The same is found like- 
wise in Dendronotus arborescens, P|. VI. figs. 8 & 9, in which the 
tentacle is remarkable for highly developed lamine ; and here the 
Ann. & Mag. N. Hist. Ser. 2. Vol. iti. 13. 
