ORIGIN OF CUBAN BLIND FISHES. 197 



ABUNDANCE OF STYGICOLA AND LUCIFUGA. 



The number of fishes in any cave differs very greatly. They are rare in caves 

 entirely inclosed ; in those entirely open and not connected with hidden recesses 

 they are also very rare or absent. They are most abundant in caves with both well- 

 lighted and dark portions and those that are continued subterraneously. The den- 

 sity of the distribution of the fishes evidently varies greatly, directly with the food 

 supply. The food supply itself varies with the openness of the cave to the external 

 world. The question arises whether the caves visited are independent pockets or 

 form part of a continuous underground system of channels, and whether the fauna 

 of the caves visited may be easily exhausted or continuously replenished from the 

 extensive subterranean channels and reservoirs. Collections made in the same 

 caves indicate that there is an undoubted decrease in the numbers and that the 

 decrease is not usually compensated by immigration from the underground reser- 

 voirs. It has rarely proved worth while to visit the same cave twice on any of the 

 stays in the cave region. The results of three visits to the "M" and Donkey 

 Caves on October 25, November 2, and December 23 illustrate the point. In 1904, 

 I secured 15 fishes in the Donkey Cave on October 25 ; 5 on November 2 ; and 3 

 on December 23. In the "M" Cave I secured 20 in March, 1902 ; 19 on October 

 25 ; 14 on November 2 ; and 9 on December 23, 1904. Equal efforts were made 

 on each occasion and an equal amount of time was given to the caves. 



On June 24, 1905, Mr. Haseman secured 4 fishes in the Donkey Cave and 7 in 

 the "M." The Donkey thus yielded 15, 5, 3, and 4 fishes respectively, on succes- 

 sive visits; the "M," 20, 17, 14, 7, 7. Both of these caves are with deep recesses in 

 which fishes could be seen but not secured. 



THE ORIGIN OF THE CUBAN BLIND FISHES. 



Without doubt the remote ancestors of the Cuban blind fishes lived in the ocean 

 and were adjusted to live in the light and to make use of it in detecting their food, 

 their enemies, and their mates. Equally without doubt, their less remote ancestors 

 became adjusted to do without light and lived in total darkness, either at a depth in 

 the ocean or more probably in the crevices in Cuban coral reefs. If in the former, 

 they entered the subaqueous exits of Cuban rivers ; if in the latter, they are older 

 than the rivers themselves, having remained in their original habitat in the crev- 

 ices of the coral reefs as these were elevated to their present and even greater 

 heights. 



The latter seems to me the more plausible theory. The fresh-water blind fishes 

 of Cuba are as old as the parts of Cuba they inhabit. They are part of the result 

 of the formation of the island. 



The deeper recesses of the crevices and rents in the naked reef at the Carboneria 

 already described are probably now inhabited by fishes of some sort, possibly by 

 Ogih'ia among others. Attention has been called to the fact that within less than 

 a quarter of a mile from them, in a coral reef raised only 4 feet above the ocean-level, 

 there is a rift essentially like those found in the naked reef skirting the ocean. This 

 rift contains fresh water, and blind fishes are abundant at a place where a circular 

 opening has been cut to form a well. 



It is entirely within the range of probability that the ancestors of these fishes 

 lived in this rift when it was 5 feet lower and contained salt water and that they 



