400 



EMBRYOLOGY OF INSECTS AND MYRIAPODS 



represents the light-sensitive part; the basal portion of the retinal cells, 



the connection with the optic-nerve neurons surrounding the eye bulb. 



The Dorsal Organ. — About the time that the germ band flexes, a 



crescent-shaped thickening appears in the ectodermal memhrana dorsalis 



Fig. 356. — Scolopendra dalmatica. Section of eye of adult, {cut) Cuticula. (erf) 

 Ectoderm. {It) Lentigene cells, (op. n) Optic nerve, {rbd) Rhabdome. {Adapted from 

 Heymons.) 



splm <M.^^^ 



Fig. 357. — Scolopendra <l 

 {ent) Entoderm, {g cod) Cjumdl 

 {Adapted from Heymons ) 



1 11 {hi} Blood cell (cW) Cardioblast. 

 vAy Heait {splm) Splanchnic mesoderm. 



a short distance in front of the head, the concave side proximad. This 

 is the dorsal organ made up of several layers of cells. After a time the 

 cells of the organ, except for the outmost layer, begin to degenerate. 

 Numerous entodermal cells gather below it, and they, together wnth an 

 occasional yolk cell, without doubt absorb the degeneration products. 



