THE HALTERES OF THE BLOW-FLY. 613 
supporting the chordotonal thread is probably developed from 
the cell protoplasm. 
Lee’s Chordotonal Organ.—Lee correctly describes a remark- 
able organ situated on the under and posterior part of the 
scabellum (Pl. XLII., Fig. 2,7). This organ consists of a thin 
dome of integument containing a sensory ganglion surmounted 
by a number of minute sensory rods, 3 » to 4 » in diameter, or 
even less, containing exceedingly minute chordotonal threads. 
Lee [299, p. 368] says: ‘The nerve to the halter divides 
as soon as it enters the base into four principal branches ; one 
enters a ganglion (bouquet) of great fusiform cells, and sup- 
plies the organs of the basal plate; two others pass in the 
halter beyond this ganglion, and, diverging from each other, 
enter ganglia similar to that of the basal organ and terminate 
in the scapal organs; whilst a fourth and smaller branch quits 
the principal trunk on a level with that to the basal ganglion, 
passes to the opposite side of the halter, and enters a ganglion 
formed at its proximal end of great fusiform cells with large 
nuclei; beyond these there is a mass of minute nuclei, and then 
a layer of minute highly refractive bodies in the form of stylets, 
and a second layer of minute nuclei immediately below the 
hypodermis. Transverse sections show the structure of this 
organ better, which in these appears as a perfectly normal 
chordotonal organ, one may say a typical one. The fusiform 
cells are the ganglion cells, the proximal mass of small nuclei 
represent the basal nuclei, the typical chordotonal elements, 
stylets or forks are the scolopifera (Nervenstifte, scolopale 
Kérperchen), and the small distal nuclei the distal nuclei of 
Graber. Inall these points the organ differs in no respect from 
chordotonal organs in general. The stylets only demand 
special consideration.’ 
‘It is well known that Leydig [269] described two kinds of 
stylets in the nerve terminations of the halteres—a slender 
form with acuminate capitella, and a thick form with rounded 
heads ; these two forms are not found intermixed, but arranged 
in two bundles. so that the slender stylets, about a dozen, 
form a group well separated from the far more numerous 
