72 THE LARVA OF THE BLOW-FLY. 



tures in the larva of QEstrus, and suggested that they are 

 probably eyes. That the larva of the Blow-fly is extremely 

 sensitive to light is certain. 



These eye-like organs (Fig. 12, / and 2) resemble the simple 

 eyes of the leech, but are devoid of pigment. The two in 

 each maxilla are situated on branches of the same nerve, each 

 is surrounded by a delicate reticular capsule, and is capable of 

 retraction. The epiostracum forms a thin, transparent cap 

 over the surface of the nerve terminals, which are long rod -like 

 cells, with a distinct layer of stellate and fusiform ganglion 

 cells between them and the nerve. 



The majority of the cutaneous nerves apparently end in the 

 cells of the hypodermis (Fig. 12, 3) in demilunes of granular 

 protoplasm (see Histolog}^, and many of these exhibit a re- 

 markable form of peripheral ganglion, first described by 

 Viallanes, and called by him ' Ganglion a cotes de melon.' 

 The ganglia are small groups of unipolar cells attached to the 

 sides of the nerves. The cells present a striking analogy with 

 those of the root ganglia of the spinal nerves of vertebrates. 



9. THE IMAGINAL DISCS, 

 a. General Morphology. 



The Imaginal discs have been already referred to (pp. 3 and 

 21) as the structures from which the nymph is developed. 



Bibliography :— 



^ 31. Lachat et Audouin, ' Anatomic d'une larve apode trouvde dans le 



Bourdon des Pierres.' Journ. de Physique, de Chimie, etc. Tom. 



Ixxxviii., p. 228, 1819. 

 ^ 32. DUFOUR, Leon, 'Etudes Anatomiques et Physiologiques sur une 



Mouche.' Mem. Pres. a I'Acad. des Sc, Math, et Phys. Tom. ix., 1846. 

 33. Weismann, a., 'Die Metamorphose der Corethra plumicornis.' Zeitsch. 



f. w. Zool., Bd. xvi., 1866. 

 "--/ 34. Ganin, M., 'The Post- Embryonic Development of Insects.' In 



Russian. Transactions of the 5th Congress of Russian Naturalists. 



Warsaw (1875), 1876. (S'yezd Russkikh EstestvoTspuitatelei Trudui 



V. Varshavye.) Resume in German, Zeitsch. f. w. Zool., Bd. xxviii., 



pp. 386-389, 1877 ; and Jahrb. d. Anat. u. Phy., Bd. v., p. 507, 1878. 

 \S 35. Dewitz, ' Beitrage zur Kenntniss der Postembryonalen Entwicklung 



der Gliedmassen bei den Insekten.' Zeitsch. f. \v. Zool., Bd. xxx., 



Suppl., 1878. 



