NOTES AND MEMORANDA. 47 



Professor Graber expresses his doubt as to the auditory nature of 

 the structure discovered by Leydig in the halteres of certain Diptera, 

 and also dissents from tlie views of the same authority as to the 

 olfactory functions of the special rod-like appendages found by him 

 on the antennae of many Arthropods. 



Plate IV. Fig. 1. — -Eight antenna of SyijyJms halfeatus, Deg. (in 

 optical section). I., II., III., the three segments ; St, Integument 

 of epicranium ; N, Antennary nerve ; n', n^, 7?-ni aud n,y, its first, 

 second, third, and fourth branches ; m, m^, Muscles of the basal 

 segment ; Tr, Trachea ; tr, its vesicular dilatation in the 

 terminal segment ; ga, Ganglia at the base of the articulated 

 hairs ; g, Joint between the second and thii-d segments ; O, 

 Opening in the same, through which the antennary nerve 

 passes ; gc, Auditory sac surrounded by its epithelium and 

 tunica propria ; a, Wall of the terminal segment, with the 

 investing liairs and the roots of the articulated hairs. Am- 

 plification iy^ Zeiss Immers. L. 

 Fig. 1 a. — The otocyst (in optical section). /J/, Auditory hairs ; 

 hp. Hair-plates ; hpo. Pore-canals in the wall of the chitinous 

 capsule corresponding to the auditory hairs ; Z, Epithelial cells 

 of the auditory sac ; tp^ Tunica proj)ria. Amplification ^—~- 

 Zeiss Immers. L. 

 Fig. 1 h. — The chitinous capsule of the otocyst (surface view). 

 w. Wall ; Tip, Hair-plate ; li, Root of the auditory hair ; hg, Hair- 

 pit ; fu, Furrow between the hair-plates. Amplification -^-^-^ 

 Zeiss Immers. L. 

 2. New Organ in the Larva of a Fly (Plate IV. Fig. 3). — In this 

 case the main structure was made out by simply placing the trans- 

 parent maggot under the compressorium. The organ in question is 

 situated in the middle line of the dorsal side of the body, immediately 

 posterior to the line of junction between the ninth and tenth segments. 

 It is a pear-shaped sac, • 3 mm. in length, with its narrow posterior 

 end produced into a fine tube. It seems probable that tube and sac 

 together are formed as an invagination of the external surface. 



The sac and tube are made of a layer of epithelial cells, covered 

 externally by a tunica propria, and lined within by a chitinous 

 cuticle which bounds their lumen. Within the sac are contained four 

 pairs of black opaque bodies of an irregularly rounded form, and sus- 

 pended by hollow stalks. The first two pairs are of about equal size, 

 being • 03 mm. in diameter. The length of the stalk is • 026 mm., 

 and its breadth at the point O'OOIS. The third and fourth pairs are 

 smaller, and are only 0' 02 mm. Probably the bodies themselves are 

 also hollow, and have very thick, strongly chitinized walls, but their 

 exact structure could not be made out, as they remained perfectly 

 opaque even after treatment with potash. The most anterior pair of 

 these bodies are attached, like berries, to the front wall of the sac; 

 immediately behind tliem is a chitinous partition separating this 

 anterior segment of the sac from the remainder. The second pair 

 are not attached directly to this partition, but to the front wall of a 

 special cellulose capsule (Binucnsack), quite separate from the true 



