AND CAVERN LIFE OF THE OHIO VALLEY. 363 



our knowledge of the relations of organic species if it could be definitely determined that 

 these whitened, sightless cavern forms could or could not breed with the ordinary external 

 varieties. 



To sum up the conclusions which may be drawn from the discussion of the antiquity of 

 caverns and cavern life, we may say that these structures are jirobably of no great age, and 

 that the life within them gives no evidence of great antiquity in its origin, and that it is 

 quite within the evidence to suppose that most of the species now living within the caves 

 are pretty constantly reinforced from without. 



In closing, it may be remarked that this continent presents an admirable field for the 

 study of the whole range of questions connected with the organic hfe of caverns. In New 

 York State we have caves which have received the full force of glacial action as far as any 

 caves can. In the Ohio valley, a vast system that has perhaps received the secondary 

 effect of ice, and possibly been covered by ice in remote times, but not during the last gla- 

 cial period. In Mexico and Cuba we have caverns which have certainly never been ice 

 covered ; so that any phase of the question can be easily examined. The Geological Sur- 

 vey of Kentucky has already examined the fauna' of about fifty caverns. The animals 

 from the caves are now in the hands of Piofessors Packard and Putnam, and the gentlemen 

 they have associated with themselves in their researches. On their uivestigation it is hoped 

 that their special researches may throw inqiortant light on the history of these foiTus. The 

 conclusions which I believe warranted b^- the considerations already adduced, may be 

 summed wp as follows : — 



1. The extensive develojmient of caverns in the Ohio valley is probably a compara- 

 tively recent phenomenon, not dating fiuther back than the latest tertiarj- period. 



2. It is do\ibtfid whether there has been any extensive development of cavern life in 

 this region before these caverns of the sub-carboniferous Imiestone began to be excavated. 



o. The general character of this cavern life points to the conclusion that it has been 

 derived from the present fauna. 



4. The glacial period, though it did not extend the ice sheet over this cavern region, 

 must have so pi-ofoundly aflected the climatal conditions that the external life could not 

 have held its place here in the shape we now find it, but must have been replaced by 

 some more arctic assemblage of species. Under the circumstances, it is reasonable to sup- 

 pose that most, if not all, the species found in these caves have been introduced since the 

 glacial period. 



5. We are also warranted by the fiicts in supposing that there is a continued infusion of 

 blood from the outer species taking place ; some of the forms showing the stages of a con- 

 tinual transition from the outer to the inner forin.^ 



^I propose hereafter to discuss the bearings of all the and shall then consider the special questions connected with 

 facts dei-ived from cavern life on the doctrine of evolution, the fishes of the cave, the question of their marine origin, etc. 



