418 C. GORDON HEWITT. 



represented by the regions lateral to the oesophageal foramen, 

 and from the anterior side of each of them arises a pharyn- 

 geal nerve (figs. 1 and ll,p/i.7?.). From the ventral side of 

 the suba3Sophageal ganglia a pair of nerves — the labial nerves 

 (fig". 1, Ih.n.) — arise and run down the proboscis, innervating 

 the muscles of that organ; on reaching the oral lobes tbey 

 bifurcate and branch freely, supplying the numerous sense 

 organs in those structures. Tlie cortical cells (Leydig's 

 " Punktsubstanz "), which fill up the spaces between the 

 ganglia and form an investing sheath round the whole gang- 

 lionic mass, are of two kinds. The smaller cells are rounded, 

 their nuclei are large in proportion to the protoplasm, and 

 their protoplasmic fibres anastomose with each other. Among 

 these smaller cortical cells, and also occasionally in the 

 ganglionic substance, larger ganglionic cells occui', their 

 protoplasm taking the stain very readily. Unipolar, bipolar, 

 and tripolar ganglion cells are found. 



The eyes. Each eye contains about 4000 facets. They 

 are similar in all respects to the eyes of the blowfly, which 

 have been fully described by Hickson (loc. cit.), whose 

 results my study confirms; consequently, a description of 

 their structure will not be given. It should be noted that, in 

 spite of the fact that Hickson corrected many mistaken views 

 held by Lowne in his memoir (1884), these are repeated in 

 his monograph of the Blowfly. 



The cephalo-thoracic nerve cord (fig. 11, en.) unites the 

 cephalic and thoracic ganglia. Near its junction with the 

 thoracic ganglion a pair of cervical nerves {cer.n.) arise, 

 innervating the muscles of the neck. 



The thoracic ganglion (figs. 12 and 14) is pyriform, with 

 the broad end anterior, and rests on the entothoracic skele- 

 ton of the mesothorax. As in the cephalic ganglion, the 

 component ganglia are ensheathed in a cortical layer, which 

 is of the same nature. The nerves of the three pairs of legs 

 {p7\cr., ms.cr., mt.cr.) arise from three large ganglia, which 

 are the prothoracic [Fr.G.), mesothoracic (Ms.G.), and meta- 

 thoracic {Mt.Q.) ganglia. These are united by a median 



