PACKARD ON A NEW CAVE FAUNA IN UTAH. 167 



inheritance. This seems indirect proof that cave faunae are of compara- 

 tively recent origin. In the production of these cave species, the ex- 

 ceptional phenomena of darkness, want of sufficient food, and unvary- 

 ing temperature, have been plainly enough verce causce. To say that the 

 principle of natural selection accounts for the change of structure is no 

 explanation of the phenomena; the phrase has to the mind of the writer 

 no meaning in connection with the production of these cave forms, and 

 has as little meaning in accounting for the origination of species and 

 genera in general. Darwin's phrase "natural selection "or Herbert 

 Spencer's term "survival of the fittest" expresses simply the final re- 

 sult, while the process, the origination of the new forms which have 

 survived, or been selected by nature, is to be explained by the action of 

 the physical environments of the animals coupled with inheritance- 

 force. It has always appeared to the writer that the phrases quoted 

 above have been misused to express the cause, when they simply ex- 

 press the result of the action of a chain of causes, which we may with 

 Herbert Spencer call the "environment" of the organism undergoing 

 modification ; and thus a form of Lamarckianism, greatly modified by 

 recent scientific discoveries, seems to meet most of the difficulties which 

 arise in accounting for the origination of species and higher groups of 

 organisms. Certainly, " natural selection" or the "survival of the fittest " 

 is not a vera causa, though the "struggle for existence" may show us 

 the causes which have led to the preservation of species, while changes 

 in the environment of the organism may satisfactorily account for the 

 original tendency to variation assumed by Mr. Darwin as the starting- 

 point where natural selection begins to act. 



In our examinations of cave animals, from extensive material collected 

 in the Middle States, and not yet wholly worked up, we find that a life 

 of perpetual darkness, and j^erhaps the want of sufficient food, as well 

 as other physical agencies, cause animals to vary either in color, the 

 general proportions of the body, the length of the mouth-parts and 

 legs, the distinctness of the joints of the appendages, where the posses- 

 sors are articulated animals, and the greater or less modification of the 

 eyes. These modifications occur in different degrees in different species 

 or genera, but the sum of the change in the environment due to an in- 

 troduction into a cave acts differently on the different forms, depend- 

 ing most probably on the out-of-door habits of their ancestors, but re- 

 sulting in either (a) the production of what is usually called a distinct 

 variety, or (&) a distinct species, or (c) a distinct genus. No cave form, 

 vertebrate or invertebrate, has, so far as we are aware, yet occurred 

 which could not have been derived from forms existing out of the cave ; 

 or, in other words, all are, as a rule, for there is a notable exception in 

 the case of the blind fish, related more or less closely to organisms exist- 

 ing in the vicinity of the caverns. 



