Page:Popular Science Monthly Volume 45.djvu/112

100 than a year, and instances of the survival of unios without moisture for long periods are not rare. While living in south Florida I discovered a colony of unios in a small drain that ran through the pine woods and which only contained water during the rainy season—some three months in the year. Thousands of these mussels were found in the channel among bulrushes, buried vertically an inch or so below the surface in nearly dry soil, with the anterior end downward, and the slightly moist, sandy banks in many places were full of them. The colony extended some ten or a dozen yards along this drain; not a specimen could be found either above or below this space, and the species was not found in the little stream into which it emptied.

A lot of these unios were taken home and laid in the garden, where they remained more than three months wholly unprotected from the hot autumn sunlight during the dry season, and when opened a number of them were found to be alive. Yet ordinarily the want of water causes the Unionidæ to speedily die. The summer of 1886 was one of the least rainfall ever known in the upper Mississippi Valley, and many streams and ponds went dry that had never been known to be so before. At this time I collected in northern Illinois and Iowa, and in every instance where the water had evaporated I found the mussels dying by thousands, though in many cases the mud was too soft to bear the collector. While collecting in the Indian Territory I visited a large pond near McAllister that had just been drained, and, although the water stood everywhere in pools, yet the Unionidæ were apparently all dead and gaping open, and the stench was so horrible that the struggle between duty and comfort was a severe one. For years I have watched the dredging operations in the Potomac at the capital, as the mud was thrown out on the flats, and in every case the mussels were dead before it was firm enough to be trodden on.

I do not believe in building a theory on too slight a foundation of fact, but I am of the opinion that these unios which have been kept dormant for lengthened periods out of water inhabited streams or ponds that were intermittent. The instance I have given in Florida is a good one, and the mussel Dr. Gray received from Australia is no doubt another. The whole island is noted for heat and long-continued droughts, and with scarcely an exception the streams and lakes go dry during the rainless season. Even the Murray River, the largest stream in the country, and ordinarily navigable for hundreds of miles, sometimes ceases to flow altogether.