598 THE SENSES AND SENSORY ORGANS. 
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 hemal 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 
Fic. 74.—A diagrammatic comparison of the outer hair-cells of Vertebrates with the 
chordotonal organs of Arthropods, copied from Graber [286]. 
A. A diagrammatic representation of one of the outer hair-cells of the organ 
of Corti after Waldeyer : a, hair-like processes ; 6, the hair-cell; ¢c, nerve fibril ; 
*, minute granule of doubtful nature; d, supporting cell ; ¢, basilar membrane ; 
JS, reticular membrane. 
B, A diagrammatic representation of a primitive chordotonal organ, after 
Graber : a, outer integument of the larva; 4, chordotonal organ ; ¢, nerve fibre 
and ganglion cell ; ¢, chordotonal ligament ; x, chordotonal thread, which Graber 
compares with .x 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. 
