614 



THE SENSES AND SENSORY ORGANS. 



thick-set stylets which are found in another part of the 

 ganglion. 1 



Lee's description of this organ, so far as my observations go, 

 is correct ; but he was quite wrong when he denied the chordo- 

 tonal character of the end organs in the scalas and cupola. I 

 can only explain this on the supposition that he worked with 

 imperfectly fixed specimens, as it is only occasionally that 

 sections exhibit the chordotonal organs of the cupola and 

 scalae, and it is probable that the chordotonal threads are 

 easily torn away by the razor in cutting the sections. 



The various appearances presented by the chordotonal 

 organs of the halteres are very difficult to understand. That 



FIG. 80. Three groups of chordotonal organs from the halter of a Blow fly, seen 

 with a \ inch objective. ./, from tin- cupola; />', from Lees organ ; and C, 

 from the scala inferior and adjacent integument. 



there are two kinds is indubitable, and in general the slender 

 rods are found in the smaller groups, whilst those of the 

 cupola and scape arc the larger form. In some sections, 

 evidently through the scala inferior, I have observed small 

 chordotonal organs in groups (Fig. 80). These are, I be- 

 lieve, only found close to Lee's organ. 



c. On the Functions of the Halteres. 



The halteres have been regarded by various authors as 

 (i) sound-producing organs; (2) olfactory organs; (3) organs 



