

420 COMPOUND VISION AND MORPHOLOGY OF EYE IN INSECTS. 



Fig. 58. A portion of the retina of a Blow-fly, from a specimen prepared with chloral hydrate, and 

 stained with eosin. 



59. A portion of the retina of the Blow-fly, osmic acid. 



60. A portion of the retina of a Blow-fly, Midler's fluid. 



61. A transverse section of a portion of the retina of a Blow-fly, from a specimen prepared with 

 Midler's fluid and mounted in balsam. 



62. A transverse section of a portion of the retina of a Blow-fly, through the inner segments of the 



bacilla, from a specimen preserved in chloral hydrate and subsequently mounted in balsam. 



63. Two fasciculi of bacilla, from a Hawk-Moth pupa. 



64. Bacilla of a Blow-fly, showing the lenticulus, from an osmic-acid preparation. 



65. Bacilla from the eye of a Cockroach, with double outer segments. 



66. Similar bacilla, from the eye of a Blow-fly. 



67. Bacilla from the eye of a Noctuid Moth. 



68. Tracheal vessels on the inner surface of the membrana basilaris of the Blow-fly. 



69. Retinal pigment-cells and a portion of the basilar membrane of a Dragon-fly (JEshnia grandis). 



70. A portion of the basilar membrane from the eye of a Lobster, showing prismatic thickenings 

 at the inner extremities of the great rods. 



71. A portion of the retina and basdar membrane of the Cabbage Butterfly, showing lenticular 

 thickenings. 



72. A vertical section through the basilar membrane of Syrphus, showing the cellular sheaths of 

 the fasciculi of bacilla, and the cells around the necks of the expanded tracheal sacs of the 

 dioptron. 



73. The disk from which the retina originates, from a Lepidopterous larva (Noctuid) . 



74. Two segments of the dioptron, with their retiuulae, from the eye of a perfect Gnat {Corethra 

 plumicornis) : 74 a. A transverse section through the inner extremity of the cone of the same ; 

 74 b. A transverse section through the spindle of the same. 



75. A portion of the dioptron of the larva of the same insect. 



76. A section of a portion of the eye of a young Gnat larva. 



77. A portion of the dioptron of an immature Crane-fly (Tipula oleracea), which had just escaped 

 from the pupa. 



Note. — Since the above was sent to press, my attention has been drawn to a short 

 paper by Justus Carriere of Strassburg (Quart. Journ. of Micros. Sci. Oct. 1884, p. 673), 

 " On the Eyes of some Invertebrata," in which my retinal layer is figured. He speaks 

 of it as the " palisade layer." He remains, however, a disciple of established views, and 

 has not given the retinal layer nearly so much attention as it deserves. So far as his 

 observations go, they appear to me to confirm my own, as I firmly believe that 

 M. Carriere, on further investigation, will be led to admit the validity of my views. 



