156 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate XXIV. 



Fig. 1. Section though the head and brain of Cermatia forceps ; op. g., optic ganglion ; com., commissures. 



Fig. 2. Section through the head of Bothropolys, showing the optic ganglion (op.g.), optic nerves {op. «.),and eyes. 



Fig. 3. Longitudinal section through the head of Psendotremia cavernarum ; pel, procerebral lobes or brain ; sub<e. 



•subcesophageal ganglion ; com., commissure leading from it ; n., nerve from the central nervous system to the 



first pair of legs. 

 Fig. 4. The same passing through one of the eyes, and showing four of the facets; ant. I., antenualor olfactory lobes ; 



ant. n., nerve to the antenna; m., mouth. 

 Fig. 5. Transverse section through the head and brain of the same, showing no traces of an optic nerve. 

 Figs. 6 and 7. Transverse sections through the same specimen ; oh I., olfactory lobe. 

 Fig. 8. Horizontal section through Pseudotremia cavernarum passing through the eyes and showing' the absence of 



the optic nerves ; sg., salivary glands; st., stomach. 

 Fig. 9. The same, drawn from a different section ; pre., brain ; suboe. g. subcesophageal ganglion. 

 Fig. 10. Portion of Fig 9, passing through one eye highly magnified, to show at gang, c, that the ganglion-cells im- 

 pinge directly upon the eye, the optic nerve being atrophied, unless the fibers or myeloid substance atop. n. 



be the atrophied remains of the optic nerve. Four facets are cut through; lit/., hypodermis, passing at 



ret. into the retina. 

 Fig. 11. Another section through the same ; the brain, or optic ganglion, reaching to near the eye, but with no true 



optic nerve. 

 Fig. 11a. Section through the eye on one side; my., myeloid substance; gc, ganglion cells; c, coues ; ret, retina. 



(The figure is too heavily shaded, and does not do justice to the author's drawings.) 

 Fig. 12. Transverse section through the same. 

 Fig. 13. The section succeeding that represented by Fig. 12. 



All the figures drawn by the author with the camera. 



Plate XXV. 



Fig. 1. Pseudotremia cavernarum. — Horizontal section through the head and brain; ant., .antenna; «., oesophagus; 



sg., subcesophageal ganglion. 

 Fig. 2. Section through the same farther in front and passing through the olfactory lobes (ol. I.); antennal nerve 



(ant. n.); c, I., commissural lobes. 

 Figs. 3, 4-10. Scoterpes copei, sections through the head and brain, showing the entire absence of optic ganglia, 



optic nerves, and eyes ; g.c, ganglion cells ; p. c, procephalic lobe. 

 All the figures drawn by the author with the camera. 



Plate XXVI. 



Figs. 1-12. Crangonyx vitreus, from Mammoth Cave. Sections through the head and brain, to show the absence of 



the optic ganglia, optic nerves, and eyes. 

 Fig. 13. Section through the head and brain of Gammarus maexdatus to show the well-developed optic ganglia and 

 nerves, with the eyes; op. I., optic lobes. 



All the figures drawn by the author with the camera. 



Plate XXVII. 



Fig. 1. Brain of Geophilus. After Newport. 



Fig. 2. Brain of Polydesmus complanatus, showing, as in Fig. 1, the entire absence of optic lobes and optic nerves ; these 



myriopods being eyeless. After Newport. 

 Fig. 3. Scoterpes copei. Side view, enlarged. After Emerton. 

 Fig. 4. Polydesmus cavicola Pack.; dorsal and lateral view; a, antenna; b, section through the body ; c, dorsal view 



of two segments, showing the tubercles on the surface ; d, end of the body, side view. Emerton del. 

 Fig. 5. Camtarus (Orconectes) pellucidus, form inermis. After Cope. 



