THE EVIDENCE OF THE AUDITORY APPARATUS 37 1 



cliitinous tubule in the other, just as the membrana tcctoria and the 

 otoliths act in the case of the vertebrate ear. 



Patten says that the only organs which seem to him to be compar- 

 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 

 ecpuilibration, 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. 1 At present such reasons 

 are based entirely upon the structure of the organs ; experimental 



1 " The Origin of Vertebrates, deduced from the Study of Ammoccetes." Part X., 

 "The Origin of the Auditory Organ : the Meaning of the VHIth Cranial Nerve." 

 Journ. Anat. and Physiol., vol. 36, 1902. 



