5 8 POPULAR SCIENCE MONTHLY. 



This view accounts also for the wide distribution of the blind 

 fishes. The ancestry of the Amblyopsidse we may assume to have 

 had a tendency to seek dark places wherever found, and incipient 

 blind forms would thus arise over their entire distribution. The 

 structural differences between Troglichthys and Typhlichthys argue 

 in favor of this, and certainly the fearless, conspicuous blind fish 

 as at present developed would have no chance of surviving in the 

 open water. Their wide distribution after their present charac- 

 ters had been assumed, except through subterranean waters, would 

 be out of the question entirely. The same would not be true of 

 the incipient cave forms when they had reached the stage at pres- 

 ent found in Chologaster. It will be recalled that Chologaster, 

 and even the blind forms, have the habit of hiding underneath 

 boards and in the darker sides of an aquarium. These dark-seek- 

 ing creatures would, on the other hand, be especially well fitted 

 to become distributed in caves throughout their habitat. S. Gar- 

 man's able argument for the single origin and dispersal of the 

 blind fishes through epigsean waters was based on the supposition 

 that the cis-Mississippi and trans-Mississippi forms were identical. 

 The differences between these species are such as to warrant not 

 only that they have been independently segregated, but that they 

 are descended from different genera. The external differences 

 between these species are trifling, but this was to be expected in 

 an environment where all the elements that make for external color 

 marking are lacking. The similarity between Typhlichthys and 

 Amblyopsis is so great that the former has been considered to be 

 the young of the latter. 



Judging from the structure of the eye and the color of the 

 skin, Troglichthys has been longest established in caves. Am- 

 blyopsis came next, and Typhlichthys is a later addition to the 

 blind cave fauna. 



" Those," said Dr. J. N. Langley, in his sectional address on Physiol- 

 ogy at the British Association, "who have occasion to enter into the 

 depths of what is oddly, if generously, called the literature of a scientific 

 subject, alone know the difficulty of emerging with an unsoured disposi- 

 tion. The multitudinous facts presented by each corner of Nature form 

 in large part the scientific man's burden to-day, and restrict him more 

 and more, willy nilly, to a narrower and narrower specialism. But that 

 is not the whole of his burden. Much that he is forced to read consists 

 of records of defective experiments, confused statement of results, weari- 

 some description of detail, and unnecessarily protracted discussion of 

 unnecessary hypotheses. The publication of such matter is a serious 

 injury to the man of science ; it absorbs the scanty funds of his libraries, 

 and steals away his poor hours of leisure." 



