ORIGIN OF CAVE FAUNA. 13 



Second process : The second theory is that of Herbert Spencer : 



The existence of these blind cave animals can be accounted for only by supposing that their 

 remote ancestors began making excursions into the cave, and, finding it profitable, extended them, 

 generation after generation, farther in, undergoing the required adaptations little by little. — Popu- 

 lar Science Monthly, xliii, 487 and 488. 



I can offer no objection to this theory. It presupposes the existence of caves, 

 and it is perfectly possible that many cave animals have arisen in this way. The 

 abundant twilight fauna in the entrance of caves argues in favor of it. Spelerpes 

 macidicaiida and other salamanders, which are so frequently found a short dis- 

 tance within caves and even in remote recesses, seem to be present colonizers that 

 bear out Spencer's view, though it is possible that these should be grouped with the 

 animals next to be considered. 



Spelerpes maculicauda has not yet been affected, as far as its structure is con- 

 cerned, by its habits. It is a nascent cave form that may result in the future in 

 a single blind species of wide distribution, or a number of species in the groups of 

 caves that are geographically separated from each other. There can be no question 

 whatever, in its case, about an accidental carrying into caves, for if it enter caves 

 by accident it must be continually meeting accidents through a very wide region. 



Third process: This view was first expressed by Garman (Science, Oct. 28, 1892, 

 p. 240): 



The originals of the cave species [non-aquatic, especially] of Kentucky were probably already 

 adjusted to a life in the earth before the caves were formed * *. 



The writer ' independently came to the same conclusion. 



This theory makes the cave simply the collecting ground of animals adapted 

 to a cave existence, and leaves the origin of this adaptation an open question. Gar- 

 man imagined that the animals become adjusted to cave existence in crevices of 

 rocks. Since these crevices are but caves on a small scale, his suggestion simply 

 tends to account for the aggregation of the animals found in the caves of Kentucky, 

 not for their becoming cave animals in the first instance. 



If at this point we might call mutation to our aid, we would have a satisfactory 

 explanation. If mutants arose among any species of animals adapted to cave 

 existence, they would find their way into caves or crevices if such existed. What 

 would happen if there were none need not concern us. But while mutation might 

 account for the positive adaptive modifications in cave animals, it does not account 

 for the negative or degenerative changes, and the more venerable theory of special 

 creation is of equal potency. 



Fourth process: It is certain that in some cases cave animals have developed 

 concomitantly with the caves. It seems quite possible that in more cases than 

 we have thought the adaptation of an animal to a very complex environment can 

 only be explained as the result of concomitant development of environment and 



1 In answer to the statement made by Eigenmann, Krause [Promethius, No. 457, p. 652, 1898] said: "Nicht 

 weil sie in dunklen Hohlen leben, seien ihre Gesichtsorgane verkummert, nicht die Entziehung des Lichtes habe 

 diese Organe zuriickgehen lassen, sondern umgekehrt, weil sie sich schon in der Oberwelt dem Leben ohne Licht 

 angepasst hatten, waren sie wohl vorbereitet gewesen, in den Hohlen, von volliger Dunkelheit umgeben, so — 

 glanzend, konnte man beinahe sagen — zu reiissiren. * * * Nun, wer's glaubt, mag ja auch bei dem Glauben 

 selig werden konnen, dass die Hohlen gleichsam zum Tummelplatz und Elysium der Blinden aller Thierklassen 

 erschaffen seien. Wir haben diese Sirenenklange aus dem mystischen Dunkel der Gegner des Lichtes und der 

 Entwickelungslehre schon rjfters gehort; sie stehen in Harmonie mit den immer starker hevortretenden Bestre- 

 bungen, dem Lamarckismus, Darwinismus und selbst dem Weismannismus ein Bein zu stellen." This quotation 

 is possibly sufficient to indicate the general tenor of the rest of his article. 



