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446
POPULAR SCIENCE MONTHLY.

ers as a fluviatile species. This genus, Io, varies greatly in different parts of the Tennessee basin. In some places it is smooth; in others, spiny; in others, long drawn out. Under a grant of the Association, Mr. C. C. Adams, of Bloomington, Ill., visited this region; travelled down one of the tributaries in a boat, collecting samples from every community of Ios; and went by train up a second river collecting at every stopping place. The results of this trip were, in a word, that in passing from the mouth to the headwaters of the two parallel tributaries the shells vary in parallel fashion and show a uniform, continuous change from the spiny, elongated condition characteristic of the mouths of the rivers to the smooth, more globose condition characteristic of the headwaters. The additional grant by the Association of one hundred dollars will assist Mr. Adams in making further quantitative studies on variation in the genus Io.

 

Hardly any fact has excited more interest among evolutionists than the blindness of cave animals; and various theories have been advanced to explain the fact. It is known that the blind condition is due to a degeneration of formerly fuctional eyes. The difficulty has been to understand what advantage is gained by losing the eyes even in a locality where eyes are of no use. It has been affirmed that 'Nature is economical' and will not expend energy in building an unnecessary organ. Weismann has suggested that the only reason why we have eyes at all is because Natural Selection is constantly weeding out poor eyes. Withdraw the necessity for good eyes, and poor eyes and good eyes will have an equal chance of surviving. According to a third theory, the functional activity of any organ is essential to its maintenance. Just as the unused arm withers so the unused eye degenerates. Of course all these theories assume that the ancestors of the blind species—for instance, of the blind fishes—had originally no inherent tendency to blindness or degeneration of the eyes. This assumption has, however, be«n recently combatted by Professor Eigenmann, who has shown that although many kinds of fish are accidentally swept into caves, only one kind has become blind: of this kind the nearest allies which live in open streams shun the light, live in crevices and under stones, and have less perfect eyes than other fishes. Some of the allies of such light-shunning fishes have made their way into caves, and have there worked out their tendency to a reduction of eyes. That has been the history of eyeless fishes. To continue the researches of Professor Eigenmann, so auspiciously begun, the Association last year granted one hundred dollars to a committee on the cave vertebrates of North America. With the aid of the grant Dr. Eigenmann has during the past year penetrated into numerous caves and obtained much additional material for his researches.

 

The American Association will meet next year at Denver, beginning on August 26th. The newly elected officers are:

 

President.

Prof. Charles Sedgwick Minot, Harvard Medical School.

 

Vice-Presidents.

Mathematics and Astronomy: Prof. James McMahon, Cornell University.

Physics: Prof. D. D. Brace, University of Nebraska.

Chemistry: Prof. John H. Long, Northwestern University.

Mechanical Science and Engineering: Prof. H. S. Jacoby, Cornell University.

Geology and Geography: Prof. C. R. Van Hise, University of Wisconsin.

Zoölogy: President D. S. Jordan, Leland Stanford Jr. University.

Botany: B. T. Galloway, U. S. Department of Agriculture, Washington, D. C.

Anthropology: J. W. Fewkes, Bureau of Ethnology, Washington, D. C.

Economic Science and Statistics;