WERNER MARCHAND 23 



Fat Body. — No observations of the fat body have been made, ex- 

 cept that Graber (1878) describes it, in Tahanus autumnalis (?), as a 

 network of pale lobes and trabecute with dendritic tracheal expansions, 

 lying dorsally and above the new organ described by him. 



Gonads. — These organs, which must be present in the larva, have 

 not been noticed or described by any author. 



Nervous System. — ^The nervous system of the larva consists, ac- 

 cording to Graber, who studied the young larva of Tabanus {Chry- 

 sops ?), of a large upper and lower cephalic ganghon, and a chain of 

 large ganglia arranged like beads and extending about half the body 

 length. According to Graber, this would be the only instance of the 

 nervous system having this structure (Plate 8, Fig. 99). 



Sense Organs. — The eyes have been mentioned; their function is not 

 clearly understood. Antennas and palpi are probably olfactory. 

 Tactile bristles occur on the body surface and have been studied by 

 Graber who finds them connected with several ganglion cells (Plate 

 8, Fig. 100, h). Chordotonal organs, similar to those in Corethra, 

 are found laterally in each segment near the surface of the integu- 

 ment, and are of the mono-, di-, and triscolop type (Graber), and are 

 connected with the trachea?. According to Graber, in small larvae, 

 the chitinous body walls themselves act as a tympanum, thus ex- 

 plaining the absence of any special tympanal apparatus (Plate 8, 

 Fig. 100, a). 



At the posterior end of the larva, situated dorsally and adjacent 

 to the blind posterior end of the heart, on the eleventh segment, is 

 an organ of unknown function, called Graber's organ, after its dis- 

 coverer (1878). It consists of a pear-shaped sac, the broader end of 

 which is anterior; the posterior end narrows down to a fine tubule 

 which opens on the integument of the body between the last and the 

 next to the last segments. Within this sac there is a series of capsules 

 set one behind the other in the long axis, and within each of these 

 capsules is a pair of small, black, pyriform bodies, each attached to the 

 anterior side of the capsule by a delicate pedicel (Plate 9, Figs. 103 to 

 108, and Plate 10, Figs. 109 to 120). These bodies diminish in size 

 from the anterior end, the first being considerably larger than the 

 rest. They are easily seen through the integument of the living 

 larva. The outer sac is an invagination of the integument, and as 



