SUMMARY. 107 



(11) The distribution of animals within a cave, aside from consider- 



ations of light and temperature, is influenced by moisture, the 

 presence of organic matter, and the presence of places of conceal- 

 ment. 



(12) Many of the species taken within a cave do not form a part of 



the true cave fauna; indeed the permanent and true cave species 

 form but a small part of the entire cave fauna, 



(13) There is no hard and fast line of division between a cave fauna 



and the outdoor fauna in the same region. 



(14) Highly modified and truly cavernicolous animals are not neces- 



sarily confined to caves, some of them occasionally being found 

 in the dark or in twilight in other situations. There are species 

 of animals adapted for cave life, but living in regions where no 

 caves exist. 



(15) Temporary residents and some of the less highly specialized of 



the permanent residents are apparently recent additions to the 

 cave fauna and local in their cave distribution. Highly special- 

 ized cave inhabitants are widely distributed and usually appar- 

 ently cave forms of long standing. 



(16) For food cave animals are directly or indirectly dependent upon 



organic matter being carried into the cave from outside. 



(17) There is a close interdependence between cave animals, so that 



if some forms were eliminated others would probably perish. 



(18) The food and habits of cave species are similar to the food and 



habits of their near relatives living in other situations. 



(19) Certain ancestral, altogether useless habits persist in cave species. 



(20) Certain dark or shade-loving groups of animals exhibit a tendency 



to become cave inhabitants. 



(21) The nearest relatives of cave forms are nocturnal, or are dark or 



shade loving species. 



(22) Accident plays no part, or at most a very small part, in the origin 



of cave inhabitants. 



(23) Animals have reached caves by active migration into places where 



they find conditions suitable for their existence. 



(24) Cave species were fitted for cave life before entering caves. 



(25) Cave species may arise from highly modified animals living out- 



side of caves going directly into the deeper parts of caves, or 

 they may arise gradually by the collecting about the mouths of 

 caves of forms slightly modified. 



(26) Cave animals possess certain characteristic modifications — more 



slender bodies, longer appendages, more abundant or more highly 

 developed sense-organs, and a retrograde development in pig- 

 ment and organs of vision. 



