SENSE-ORGANS IN ANTENNA AND PALPI OF DIPTEBA. 



55 



through the antenna of the same insect, taken under a low power. 

 It illustrates how far the pit extends into the antenna and the 

 large number of chitinous processes. Text-fig. 24 is an oblique 

 section through the roof of the pit slicing partly through the 

 chitin and exposing the pit itself. The chitin is perforated and 

 through each perforation can be seen a sensoiy process. Seri- 

 comyia horealis shows a somewhat similar condition. Text fig. 25 

 is a semi-diagrammatic representation of a longitudinal section 

 through its antenna. The only difference from the condition in 

 -X. sylvarum lies in the fact that the pit does not bifurcate. Text- 

 fig. 26 is from a transverse section of the antenna of 8. horealis, 

 showing the large pit dissociated from the rest of the tissue, with 

 a cell running to each process. The pit is surrounded by a nerve 

 and all the nuclei are confined to the parts of the cells remote 

 from the sensory processes. Text-fig. 27 is a section through the 

 opening of the lai-ge pit and the nerve is shown encircling the 

 large cells. 



OYOLORHAPHA. SCHIZOPHORA. 



SEPSiDJi: (Text-figs. 28, 29.) 



Text-fig. 28 is a drawing of a transverse section of the antenna 

 of a large undetermined Sepsid showing a sense-pit with its large 



Text-fiivure 28. 



Transverse section through the antenna of an undetermined Sepsid. X 600. 



cells and the nerve encircling them. The sensory processes are 

 bottle-shaped and drawn out to a point. Text-fig. 29 is a semi- 



