232 BLIND VERTEBRATES AND THED3. EYES. 



CONCLUSIONS IN REGARD TO LUCIFUGA AND STYGICOLA. 



i. Lucifuga and Stygicola are two marine fishes that have remained in the 

 cracks and caves of the coral beaches which they inhabited, as these caves were 

 elevated and became filled with and enlarged by fresh water. They have become 

 entirely adjusted to a fresh-water environment. 



2. Stygicola is known from both the north and south slopes from Alacranes to 

 Matanzas and Alfonso XII. Lucifuga is known only from the south slope west of 

 Havana. 



3. The caves in which the fishes were found are all well lighted, but are always 

 connected with dark underground channels. Each cave has only a limited supply 

 of fishes that may be replenished from the underground channels. 



4. Lucifuga and Stygicola are negatively heliotropic. They are adjusted to 

 withstand but slight temperature changes. They feed on crustaceans and odonata 

 larvae. 



5. Both species are viviparous, giving birth to 2 to 15 young about 25 mm. long. 

 Both probably breed throughout the year. Spermatozoa are transferred long before 

 the ripening of the eggs. Lucifuga breeds probably most abundantly through 

 March and May in shallow places. Its young are abundant near the surface. 

 Stygicola breeds in unknown places and its young are not seen near the 

 surface. 



6. The eye decreases in size progressively from birth to extreme old age con- 

 comitantly with the appearance of masses of pigment cells in the orbital fat. 



7. The eye varies greatly in different individuals of the same size — from 260 

 to 425 /tx in length, in brothers and sisters in the same ovary. 



8. The ontogenetic degeneration results either in the shriveling of the entire 

 structure or the great distention of the pigmented layer. One process may be found 

 on one side, the other on the other side of the same individual. 



9. The eye muscles are all present in the young, but undergo a variable amount 

 of degeneration with age, disappearing entirely in very old of Stygicola. 



10. The sclera is self-determining in both Lucifuga and Stygicola. In Luci- 

 fuga the cartilages at the time of birth are too large for the eye, forming a shield 

 over the face of the eye. In Stygicola it forms a ring about the middle of the eye. 

 After birth they very rapidly degenerate and disappear entirely by the time Lucifuga 

 has reached less than half its maximum length. In Stygicola it remains longer. 



n. There is evidence that there is an early disturbance of the vascular system 

 of the eye resulting in the formation of large blood lakes about the eye. 



12. The lens has begun to degenerate before birth. Its contents liquefy, the cap- 

 sule shrivels, and finally disappears at a length of about 40 mm. 



13. It has not been determined when the histogenesis of the retina ends and its 

 degeneration begins. The most highly developed retina was found in an unborn 

 young of Lucifuga 20 mm. long. In this retina the outer nuclear, outer reticular, 

 inner nuclear, inner reticular, and ganglionic layers are more or less distinctly 

 represented. 



