CONTENTS. IX 



PACK 



of Crustacea — Structure of eye — Mysis — Coryctous — Copilia 

 — Calanella — Limulus — Scorpions — Light-organs of Eu- 

 phausla— Mode of vision by compound eyes— Muller's theory 

 of Mosaic vision — Images thrown by the cornea — Objections 

 to other theories— Position of the image — Absence of power 

 of accommodation — Absence of retina- Summary — On the 

 power of vision ia insects — Experiments on vision of insects 

 — On the function of ocelli — Difficulty of subject — Experi- 

 ments—Short sight of ocelli — Ocelli of cave-dwelling spiders 

 — Probable function of ocelli ... ... ... ... US 



CHAPTEE VIII. 



On problematical organs of sense — Muciferous canals of fith — ■ 

 Deep-sea fish — Light-organs — Living lamps — Problematical 

 organs in lower animals — Medusfe — Insects — Crustacea — 

 Difficulty of problem — Size of ultimate atoms — The range 

 of vision and of hearing — Unknown senses^The unknown 

 world ... ... ... ... ... ...• 1S2 



CHAPTEE IX. 

 On bees and colors—Experiments with colored papers — Dr. 

 Miiller's objections — Reply to objections — Preferences of 

 bees — The colors of flowers ... ... ... ... 194 



CHAPTEE X. 



On the limits of vision of animals — Ants and colors — The 

 ultra-violet rays — The limits of vision in ants— Supposed 

 perception of light by the general surface of the skin — 

 Experiments with hoodwinked ants — Confirmation of my 

 iexperimeuts on ants — Experiments with Daphniae — Dapli- 

 nias and colors — Preference for yellowish green — Experi- 

 ments — Limits of vision of Daphnias — Perception of 

 ultra-violet rays — Objections of M. Merejkowski — Suggestion 

 'that Daphnias perceive brightness, but not color — Furtlier 

 experiments — Evidence that Daphnias perceive differences 

 ofcolor .,. ... ... ... ••• '•• 202 



CHAPTEE XL 



On recognition among ants — Experiments with intoxicated ants 

 — Evidence against recognition by means of a sign or pass- 

 fvord — Experiments with ants removed from the nest as 



