404 POPULAR SCIENCE MONTHLY. 



affected by the struggle for food, for stored food occupies the former eye 

 space. It could only be affected by the more active selection of specific 

 parts of food by some actively functioning organ. It is possible that 

 this has in fact affected the degeneration of the eye. The theory ex- 

 plains degeneration in the individual, and implies that the effect in the 

 individual should be transmitted to the next generation. This second 

 part seems but the explanation of the workings of the Lamarckian 

 factor. 



The Lamarckian view — that through disuse the organ is diminished 

 during the life of the individual, in part, at least, on account of the 

 diminution of the amount of blood going to a resting organ, and that 

 this effect is transmitted to succeeding generations — not only would 

 theoretically account for unlimited progressive degeneration, but is the 

 only view so far examined that does not on the face of it present serious 

 objections. Is this theory applicable in detail to the conditions found 

 in the Amblyopsidre ? Before going further, objections may again be 

 raised against the universal assumption that the cessation of use and 

 the consequent panmixia was a sudden process. This assumes that the 

 caves were peopled by a catastrophe. But it is absolutely certain that 

 the caves were not so peopled, that the cessation of use was gradual, 

 and the cessation of selection must also have been a gradual process. 

 There must have been ever-widening bounds within which the variation 

 of the eye would not subject the possessor to elimination. 



Chologaster is in a stage of panmixia as far as the eye is concerned. 

 It is true the eye is still functional, but that the fish can do without its 

 use is evident by its general habit and by the fact that it sometimes lives 

 in caves. The present conditions have apparently existed for countless 

 generations — as long as the present habits have existed — and yet the 

 eye still maintains a higher degree of structure than reverse selection, 

 if operative, would lead us to expect, and a lower than the birth mean 

 of fishes depending on their eyes, the condition that the state of pan- 

 mixia alone would lead us to expect. There is a staying quality about 

 the eye with the degeneration, and this can only be explained by the 

 degree of use to which the eye is subjected. 



The results in Chologaster are due to panmixia and the limited 

 degree of use to which the eye is put. Chologaster Agassizii shows the 

 rapid diminution with total disuse. 



The difference in the conditions between Chologaster and Amblyop- 

 sis, Typhlichthys and Troglichthys, is that in the former the eyes are 

 still in use, except when living in caves; in the latter they have not been 

 in a position to be used for hundreds of generations. The transition 

 between conditions of possible use and absolute disuse may have been 

 rapid with each individual after permanently entering a cave. Pan- 

 mixia, as regards the minute eye, continued. Reversed selection, for 



