W.-R. THOMPSON 



domesticn (/. r., p. 127 et seq., fig. 52-o4) Hewitt a étudié le 

 système nerveux au point de vue topocrapbique, d'une façon 

 suffisamment complète ; et Kkilin ('7) dans son étude des lar- 

 ves des Anthomyiides carnivores a vérifié la plupart des résul- 

 tats de l'auteur antilais. 



« The central nervous System of the larva (fig. 52), dit 

 Hewitt (^ bas attained what would appear to be the limit of gan- 

 glionic concentration and fusion. The boat-chaped ganglionic 

 mass (fig". 53), which lies partly in the fifth segment, is a compound 

 ganglion and represents the fusion of eleven pairs of ganglia 

 similar to that which Leuckart (1S58) describes in the first lar- 

 val stage of MeIo])Jifi(p(Si orinits, but which, liowever, bas not 

 undergone so groat a degree of concentration as in M. domestica, 

 Tbis ganglionic mass, which, for convenience and brevity, I 

 sball call the ganglion (Lowne's « neuroblast ») does not 

 exhibit externally any signs of segmentation, the interstices 

 ])et\veen the component ganglia being lilled up with the corti- 

 cal tissue, wdiosc outer wall forms a plain surface. In horizon- 

 tal and sagittal sections, bowever, the component ganglia can 

 be recognized and their liniits are more clearly defiiled. The 

 ganglion is surrounded by a thick ganglionic capsular sheath 

 which is richly supplied with tracheae, and appears to be con- 

 tinuons with the outer sheath of the peripheral nerves Two 

 pairs of large tracheae (lig. 53) are found entering the ganglio- 

 nic sheath, an anterior pair (/;■') which runs in betwen the 

 cérébral lobes, and a latéral pair (/r") entering the ganglion 

 beneath thèse lobes. In the young larva the cortical layer of 

 cells is proportionately nmch thicker. The cortical tissue is made 

 up of cells of varying sizes, but which can be grouped in two 

 classes — smaller cortical cells and larger ganglionic cells. 

 Most of the ganglionic cells appear to be unipolar, but there are 

 many of a bipolar and multipolar nature présent; they stain 

 readily and possess fairly large nuclei. Thèse ganglionic cells 

 are arranged segmentally, and occur near the origin of the ner- 

 ves. In the posterior région of the ganglion, where the nerves 

 arisein close proximity, the ganglion cells are very numerous, 

 relatively few of the cortical cells being found. A further 

 démarcation of the component ganglia is brought about by 

 médian and vertical strands of the ganglionic sheath-tissue, 



