THE HALTEBES AND WING ORGANS. 97 



The organs themselves have been described as openings in 

 the integument, closed by a thin convex membrane ; but the 

 appearance is deceptive, as far as I can tell, and I have 

 examined these parts with great care. There are no openings 

 in the integument, and the bright spots are entirely due to the 

 presence of lenticular corpuscles of high refractive power 

 beneath. By crushing the base of the halter in fluid between 

 the thin glass and slide, I have succeeded in seeing these 

 organs in profile, in situ (Plate VIII., fig. 6). I have been 

 unable to discover their exact connection with the integument, 

 but from the difficulty of displacing them, I suspect they are 

 contained in sacculi. When set free, which may be effected 

 by crushing the halter by a side motion of the thin glass, the 

 bright spots disappear from the ridges, which could not 

 happen if these were due to perforations ; and the corpuscles 

 appear free in the fluid. They are chiefly elongated, but a 

 few are spherical. They vary in size from l-3000th to l-5000th 

 of an inch in diameter. There are from 250 to 300 in each 

 of the basal, and about 200 in each of the proximal sets, 

 making nearly 1,000 in each halter. 



The basal part of the halter becomes contracted, and forms 

 the pedicle, which is connected with each of the two half- 

 cylinders by a hollow ridge. The pedicle is clothed with 

 fine hairs, especially at its distal extremity. It terminates in 

 the globe, which is a hollow dilatation about l-80ibh of an inch 

 in diameter. The integument of the globe is extremely delicate 

 and transparent. It exhibits rounded pigment spots of orange 

 pigment beneath it, and has several large scattered hairs upon 

 its surface. 



The interior of the globe is occupied by a number of large 

 vesicles about 1 -300th of an inch in diameter, filled with and 

 surrounded by fluid, which also fills the base and pedicle of 

 the organ. 



