2 5 



ANIMAL BIOLOGY. 



[Part II. 



seen in a dried ophthalmite under a low power. Beneath each 

 facet is the end of a crystalline cone (cr.), which narrows in the 

 deeper part of the eye, and then swells again to form a striated 



D. 



FIG. 78. CRAYFISH SENSE ORGANS. 



A. Joints near the end of the exopodite of the antenuule, showing tactile 

 setse at a and olfactory setae at &. 



B. Tactile setae. a. From the tip of the endopodite of the antennule. fc. 

 From a tuft on the antennulary protopodite. 



C. Olfactory setse. a. From the side. I. From above. 



D. Auditory seta, with grains of sand at s. 



E. Portion of section of eye. &. TO. Basilar membrane, co. Cornea, cr. 

 Crystalline cone. g. c. Ganglion cells, n. f. Nerve-fibres. re. Pigment. 

 st. sp. Striated spindle. 



F. Diagram of arthropod vision. a. 6. Transparent rods, with pigment 

 between, c. d. Object. (/. d'. Its image on the screen e. f. 



spindle or rhdbdom (st. sp.) marked with delicate transverse lines. 

 At the inner end of the striated spindles there seems to be a 

 basilar membrane (b. m.\ beneath which are the nerve fibrils 



