172 PATTEN. [ Vio‘. Woh 
(28) The three-lobed optic ganglion of the convex eye of Arthro- 
pods is derived from a three-segmented larval ganglion, each segment 
of the latter belonging to a pair of larval ocelli. 
(29) The first, second, and third segments of the optic ganglion of 
Acilius larvee are respectively homologous with the second, first, and 
third lobes of the optic ganglion of the compound eye. 
(30) Hence, from the first segment of the larval ganglion, or that 
segment which is united with the large, posterior, dorsal ocellus, is 
developed the optic ganglion proper of the compound eye. 
(31) The optic ganglion contains six medullz, each of which corre- 
sponds in structure to that of the retina to which it belongs, and this 
indicates that the arrangement of the medullary fibrillz is as near like 
that of the retinidial fibrille of the retina, as the existing condition will 
allow. . 
(32) The structure of the retina in the larval ocelli of Insects is much 
like that of Myriapods, and the whole eye is constructed on the same 
plan as that of Perzpatus and most Molluscs. 
MILWAUKEE, June 1, 1888. 
