TRANSACTIONS OF SECTION I. 963 
the brain and spinal cord, and has already been recognised as the remains of the 
liver and generative organs, does not penetrate into the velar or other appendages, 
but is found only in the auditory capsule, where it enters with and partly surrounds 
the auditory nerve. 
The coincidence is so startling and unexpected as to bring conviction to my 
mind that in the flabel/um of Limulus we are observing the origin of the vertebrate 
auditory apparatus ; and it is, to say the least of it, suggestive that in Galeodes the 
last locomotor appendage should carry the extraordinary racquet-shaped organs 
which Gaubert has shown to be sense-organs of a special character, and that in the 
scorpion a large special sense-organ of a corresponding character, viz. the pecten, 
should be found which, from its innervation, as given by Patten,! appears to belong 
to the segment immediately anterior to the operculum, rather than to that imme- 
diately posterior to it. 
Comparison of the Olfactory Organ of Ammocetes with the Camerostome of 
Thelyphonus. Meaning of the Ist Nerve. Also comparison of the 
Hypophysis with the Mouth-tube of Thelyphonus. 
In precisely the same way as the theory has led to the discovery of a special 
sense-organ in Limulus and its allies which may well be auditory, so also it must 
lead to the discovery of the olfactory apparatus of the same group, for here also, just 
as in the case of the auditory apparatus, we are at present entirely in the dark. 
The olfactory organ in such an animal as Thelyphonus ought to be innervated 
from the supra-cesophageal ganglia, and ought to be situated in the middle line, in 
front of the mouth. The mouth is at the anterior end in these animals, the lower 
lip or hypostoma (see fig. 9) being formed by the median projecting flanges of the 
basal joints of the two pedipalpi; above, in the middle line, is a peculiar median 
appendage called the camerostome. Still more dorsal we find in the median line 
the rostrum, with the median eyes near its extremity, and laterally on each side of 
the camerostome, and dorsal to it, are situated the powerful chelicerze, which are 
considered by some authorities to represent antennze. Of these parts the camero- 
stome is certainly innervated from the supra-cesophageal ganglia, and upon cutting 
sagittal and transverse sections in a very young Thelyphonus we find that the 
surface is remarkably covered with very fine sense-hairs, arranged with great regu- 
larity and connected with a conspicuous mass of large cells. Upon making trans- 
verse sections through this region we see that the camerostome projects into the 
orifice of the mouth, and that its sense-epithelium forms, together with a similar 
epithelium on the lower lip, a closed cavity surrounded by a thick hedge of fine 
hairs. Here, then, in the camerostome of Thelyphonus 1s a special sense-organ 
which, from its position and its innervation, may well be olfactory in function, or at 
all events subserve the function of taste. 
Upon comparing this organ with the olfactory organ of Ammoccetes we see a 
most striking resemblance in general arrangement and structure. 
Just as the mouth tube of Thelyphonus is formed of two parts, the pedipalp and 
camerostome, so, according to Kuppfer, the nasal tube of Ammoccetes is composed 
of two parts, the upper lip and the olfactery protuberance. Of these two parts 
we see that the upper lip, or hood, like the pedipalp, is innervated by the Vth nerve, 
or nerve of the prosomatic appendages, while the olfactory protuberance, like the 
camerostome, is innervated by the Ist nerve. Kuppfer’s investigations show us 
further (fig. 9) how the olfactory protuberance is at first free, is directed 
ventralwards, and lies at the opening of the hypophysial tube ; how afterwards, by 
the forward and upward growth of the upper lip to form the hood, the nasal tube 
is formed, with the result that the nasal opening lies on the dorsal surface just in 
front of the pineal eye. Kuppfer, like Dohrn and Beard, looks upon this hypo- 
physial tube as indicating the paleeostoma, or original mouth of the vertebrate, a 
view which harmonises absolutely with my theory, and receives the simplest of 
explanations from it, for, as you see on the screen, sections through the mouth tuhe 
' Patten, Quart. Jown. of Mier. Sci. vol. xxxi. 1890. 
