26 LAWSON, ON LIMAX MAXIMUS. 
after a slight degree of ramification, is lost in the tissue and 
muscles of the lower tentacles; the fourth and most posterior 
pair passes forwards, and, being lost upon the mouth and 
adjacent structures, deserves the name of buccal. The third 
ring we now arrive at. It is about as wide as the second 
(which measures transversely somewhat more than + inch) ; 
indeed, its upper ganglionic mass is nothing more than the 
inferior expansion of the latter (fig. 8). Its superior com- 
ponent is oblong, irregular, and not very symmetrical, 
slightly convex anteriorly and concave behind, with its 
noduliform extremities pointing forwards; it is united 
directly by fusion to the lower mass. The latter is com- 
posed of three ganglia, soldered to each other in an arciform 
manner, the concavity directed upwards. The two portions 
of this ring are so closely related, that, to the naked eye the 
existence of an intervening space is barely perceptible. It is 
from this congeries of ganglionic centres that the different 
viscera and the great pedal muscles receive their nervous 
filaments, which, though numerous at the periphery, are 
referable to five primal pairs, and an azygos central branch 
proceeding to the posterior surface of the head. The first, 
passing from the superior extremities of the mass, supplies 
the heart, part of the gullet, stomach, and the lungs. The 
divisions of this pair are peculiar, for many of the threads, 
after separation, again unite, thus forming a very rudimentary 
plexus. The second, third, and fourth pairs all originate in 
the lateral portions of the rmg, and terminate in the walls of 
the intestine, the reproductive organs, and the liver. The 
fifth pair is the most inferior, and arises from the inferior and 
internal border of the external walls of the ring, leaving a 
central and included space, from which vo nerves start. The 
nerves comprised in this couple are “the great pedal ;” they 
direct their course backward on either side of the great cen- 
tral gland (?), and beneath all the viscera, and after having 
transmitted three or four branches to the musculo-connective 
tissue of the foot, terminate at a distance of 2 inches from 
their origin, in that portion of the pedal organ, just beneath 
the ovary, and last lobe of liver. 
Histology of Nervous System, and general remarks thereon. 
—The nerves viewed under the microscope present rather the 
aspect of connective tissue than the tubular appearance 
characteristic of vertebrate nervous fibres, the outer edge of 
each individual nerve seeming denser and to have undergone 
more decided differentiation than the inner portion, On 
entering the ganglion the nerve splits up into a considerable 
