PECULIAR SENSE-ORGANS. Ill 



more nearly spherical projections from the cuticular 

 surface," and as placed in rows. The number and 

 arrangement differ in different species: the blowfly 

 (Sarcophaga carnaria) has ten rows, Syrphus luniger as 

 many as twenty. 



These organs have recently been again examined by 

 BoUes Lee.* The vesicles are, according to him, un- 

 doubtedly perforated, contain a minute hair, and those 

 of the upper groups are protected by hoods of chitine. 

 He inclines to correlate them with the similar antennal 

 organs, which he regards as olfactory. His view of the 

 minute structure of these rods differs from that of 

 previous authors, and the subject requires further 

 study. 



He finds, moreover, that the sense-organ containing 

 the rods has nothing to do with the vesicular plates, 

 but that they are attached to the cuticle in a different 

 place, and where it presents no special modification. 



The numerous small membranes in the halteres of 

 insects seem to bear somewhat the same relatioa to 

 the single tympanum of, say, the looist, as the many- 

 faceted eyes do to those with a single cornea. The 

 head of the halteres is divided into two separate 

 spaces by a membrane composed of elongated hypo- 

 dermal cells. The upper part contains a number of 

 large vesicular cells, like those which are in connection 

 with the ends of the tracheae. It does not appear 

 to contain any special sense-organ, and, in fact, tlie large 

 nerve is almost entirely devoted to the sense-organs at 

 the base. M. Bolles Lee suggests that it perhaps 

 serves principally to regulate the pressure on these 

 delicate structures. 



* " Les Balanoiers des Diptferes," Recueil Zool. Suisse, 18S5. 

 7 



