598 



THE SENSES AND SEXSOR Y OKGA NS. 



Organs. Graber compares the primitive chordotonal organs of 

 Insects with the outer hair cells of the organ of Corti in the 

 Vertebrata (Fig. 74), and remarks that in both cases the 

 vibrations act vertically upon the membranes, between which 

 the end organs are stretched. In the case of the haemal end 

 organ the analogy is still more complete, as in this case it is 

 the movement of the surrounding fluid of the body cavity, 

 which acts upon the membranes supporting the end organ. 

 The diagrams show a very complete accordance between these 

 structures in the Arthropod and the Vertebrate, and make the 

 view he has adopted very plausible. It must, however, be 

 admitted that the representation is extremely diagrammatic 

 in the case of the Vertebrate end organ, and that in details 



FIG. 74. A diagrammatic comparison of the outer hair-cells of Vertebrates with the 

 chordotonal organs of Arthropods, copied from Graber 1286J- 



A. A diagrammatic representation of one of the outer hair-cells of the organ 

 of Corti after \Yaldeyer : a, hair-like processes ; />, the hair-cell ; c, nerve fibril ; 

 -r, minute granule of doubtful nature ; </, supporting cell ; f, basilar membrane ; 

 /, reticular membrane. 



H. A diagrammatic representation of a primitive chordotonal organ, after 

 Graber: a, outer integument of the larva; />, chordotonal organ; <, nerve fibre 

 and ganglion cell ; </, chordotonal ligament ; x, chordotonal thread, which Graber 

 compares with . in Fig. A. 



the structures are very different. I think, however, that the 

 similarity is sufficient to give a very high degree of probability 

 to Graber's view that these end organs are auditory in 

 function. 



