CONTENTS. V 



The Cuban Blind Fishes — continued PAGE 



Nature of the Habitat of Stygicola and Lucifuga 1 88 



Abundance of Stygicola and Lucifuga . . . . . 197 



Origin of the Cuban Blind Fishes ........... 197 



Physical environment of Stygicola and Lucifuga and their Reactions to it . . . .198 



Biological environment of Stygicola and Lucifuga . . . . . . . .201 



General habits of Lucifuga and Stygicola .......... 204 



Breeding habits of Lucifuga and Stygicola . 204 



The Ovaries of Lucifuga and Stygicola .......... 206 



The Eyes of Lucifuga 208 



The Eyes of Stygicola .............. 220 



On the Ovary and Ova in Lucifuga and Stygicola ......... 226 



Conclusions in Regard to Lucifuga and Stygicola ......... 232 



The causes of Individual and Phyletic Degeneration .......... 233 



LIST OF PLATES. 



FACING 

 PAGE 



Frontispiece. Entrance to Ariguanabo River, Cuba. Blind-fish rocks at base of Point Loma, San 



Diego, California Title 



Plate A. Twin and Shawnee Caves ............ 6 



1 . Chologaster papilliferus, Spelerpes maculicauda, Spelerpes slejnegeri, and Typlilotriton 



spelaus ............... 12 



2. Spelerpes longicauda and Typhlomolge rathbuni 28 



3. Rhineura ftoridana ............. 48 



4. Eye of Typhlops lumbricalis ........... 54 



5. Amblyopsis ............... 70 



6. Chologaster agassizii, Troglichthys rosce, and Typhlichthys subtcrraneus ... 72 



7. Views of Amblyopsis, early stages . . . . . . . . . .92 



8. Tactile organs of Amblyopsis and Chologaster . 98 



9. Heads of Zygonectes not at us, Chologaster agassizii, Chologaster papilliferus, Typhlichthys 



subterraneus, Troglichthys rosoz, and Amblyopsis spelsus . . . . .110 



10. Photographs of the eyes of Amblyopsis and Troglichthys ...... 132 



11. Carboneria Beach near Matanzas. Cave of the Insurrectos, near the Carboneria . . 186 



12. Young of Lucifuga in Ashton Cave. Cave Isabella, showing roots .... 190 



13. Stygicola. (Preserved specimens) .......... 196 



14. Living Stygicolas 200 



1 5 . Views of Lucifuga 200 



16. Sections of eye of Lucifuga ............ 208 



17. Two sections through right eye of Lucifuga ........ 208 



18. Sections of eye of Lucifuga, showing contents of lens, capsule, and layers of retina . 208 



19. Eyes of Lucifuga, showing pigment layer and retina and folding of sclera . . . 208 



20. Eyes of Lucifuga, showing differences in size and structure ...... 216 



21. Sections through left and right eye-cavities of Lucifuga ...... 216 



22. Sections of eyes of Lucifuga, showing pigment layer and cells and oblique and rectus 



muscles . . . . . . . . . . . . . . .216 



23. Eye of old Lucifuga, showing pigment mass and fibrillar network about eye . . 216 



24. Eye of Lucifuga .............. 222 



25. Eye of Stygicolas and Lucifugas ........... 222 



26. Eye of Stygicola .............. 222 



27. Ovaries of Lucifuga and Stygicola .......... 232 



28. Sections of ovaries ............. 232 



29. Sections of ovaries 232 



