THE EVIDENCE OF THE AUDITORY APPARATUS 371 
chitinous tubule in the other, just as the membrana tectoria and the 
otoliths act in the case of the vertebrate ear. 
Patten says that the only organs which seem to him to be compat- 
able with the gustatory porous organs of Limulus are the sense-organs 
in the extremities of the palps and of the first pair of legs of Galeodes, 
as described by Gaubert. I imagine that he was thinking only of 
arachnids, for the comparison of his drawings with those of Graber 
show what a strong family resemblance exists between the poriferous 
sense-organs of Limulus and those of the insects. On the course 
of the terminal nerve-fibres, between the nerve-cell and their entrance 
into the porous chitinous canal, Graber describes the existence of 
rods or scolophores. On the course of the terminal fibres in the 
Limulus organ, between the nerve-cells and their entrance into the 
porous chitinous canal, Patten describes a spindle-shaped swelling, 
containing a number of rod-like thickenings among the fibrils in the 
spindle, which present an appearance reminiscent of the rods described 
by Graber. 
It appears as though a type of sense-organ, characterized by the 
presence of pores on the surface and a fine chitinous canal which 
opens at these pores, was largely distributed among the Arthropoda. 
According to Graber, this kind of organ represents a primitive type 
of sense-organ, which was probably concerned with audition and 
equilibration, and he expresses surprise that similar organs have not 
been discovered among the Crustacea. It is, therefore, a matter of 
great interest to find that so ancient a type of animal as Limulus, 
closely allied to the primitive crustacean stock, does possess pori- 
ferous sense-organs upon its appendages which are directly compar- 
able with these poriferous chordotonal organs of the Insecta. 
THE PECTENS OF SCORPIONS. 
Among special sense-organs such as those with which I am now 
dealing, the pectens of scorpions and the ‘racquet-organs’ of Gale- 
odes must, in all probability, be classed. I have given my reasons 
for this conclusion in my former paper.! At present such reasons 
are based entirely upon the structure of the organs; experimental 
1 « The Origin of Vertebrates, deduced from the Study of Ammoceetes.”” Part X., 
“The Origin of the Auditory Organ: the Meaning of the VIIIth Cranial Nerve.” 
Journ, Anat. and Physiol., vol. 36, 1902. 
