540 THE SENSES AND SENSORY ORGANS. 
ommatea; but when the final ecdysis occurs, a new optic 
nerve and retina is developed, which replaces all the partial 
nerves and retin of the larval form (Fig. 70). This is formed 
within the hemisphere, and grows outwards until it reaches 
the inner surface of the dioptron; the partial retinze undergo 
histolytic degeneration during its development. I think it 
Fic. 70.—The development of the retina in the compound eye of a Dragon-fly 
(Agrion) and of the Cockroach (Leriplaneta). A, a section of the eye and optic 
nerves of the larva of agrion from a specimen 12 mm. long ; 4, a similar section 
from a more advanced larva ; C, a similar section from the nymph of the same ; 
D, a section through the optic ganglion and nerve of a young Cockroach larva ; 
d, the dioptron ; g!, the ganglion from which the larval optic nerves arise; g°, 
the optic ganglion of the imago ina more or less rudimentary condition ; 7 4, 
the membrana basilaris; 7z', the retina of the larva consisting of separate 
retinule ; 77°, the retina of the imago in a more or less rudimentary condition ; 
¢y, tracheal vessel. Reproduced from my paper [233] in the Trans. of the Linn, 
Soc. 
exceedingly probable that the remarkable ‘kidney-shaped’ 
bodies described by Newton [213], in the optic ganglia of the 
lobster, are retinze and optic nerves, which replace the old 
retinz in successive ecdyses. 
Even in the Metabola there are traces of the development 
