ON THE DEEP-WATER FAUNA OF LAKE MICHIGAN.

BY DR. WILLIAM STIMPSON.

A knowledge of the character of the animals and plants living at the bottom of the great North American Lakes, the largest bodies of fresh-water in the world, has long been a desideratum; and dredging operations have this year been initiated by the Chicago Academy of Sciences which have already produced interesting results. The first dredgings were made off Chicago, where the waters were found to be shallow, and the bottom sandy or gravelly. At a distance of eighteen miles from land the depth was but fourteen fathoms. The bottom was nearly barren of life. We obtained, however, specimens of the larva of some neuropterous insect, a Clepsine, a flesh-colored leech belonging to a new genus; a Lymnaea, two Melanians and a Plumatella. The plants consisted of a moss, a Chara, a Nostoc, and one other alga.

The next investigations were made in the more central and deeper parts of the lake. Dr. Hoy of Racine had been for some time endeavoring to ascertain the nature of the food of the whitefish, which had previously remained entirely unknown. These fish being caught in gill-nets and "pounds," are generally taken from the water some hours after being actually entrapped, and the food in the stomach becomes thoroughly digested, and its character undistinguishable before it can be obtained and examined. Dr. Hoy, however, after long search, succeeded in obtaining some fish in which the contents of the stomach was in a comparatively fresh state, and ascertained it to consist mainly of remains of small crustaceans. These he submitted to me for examination, and among them I had the pleasure of detecting indications of the existence of marine forms in the lake.

It thus became highly desirable to examine the ground upon which Dr. Hoy's fishes had been obtained, and accord

ingly on the 24th of June last we started out from Racine for the purpose in a tug belonging to that place. The party consisted of Dr. Lapham, Dr. Hoy, Mr. Blatchford and Dr. Andrews of Chicago, and myself. We dredged at various points from twelve to twenty-six miles from land, the greatest depth found being sixty-four fathoms, with a bottom of blackish impalpable mud. Between the distances of twelve and twenty-two miles from shore the depth was tolerably uniform, averaging forty-five fathoms, the bottom being generally a reddish or brownish, sandy mud. On this plateau we obtained alive the crustacea found by Dr. Hoy in the stomachs of the whitefish, consisting of a Mysis and two species of Gammarus. A small white Planaria, and a new species of Pisidium also occurred. All of these animals were found in abundance, showing this portion of the lake bottom to be rather densely inhabited.

seas.

Mysis is a marine genus, many species of which occur in the colder parts of the North Atlantic and in the Arctic One species, M. relicta, was found by Lovén in company with Idothea entomon and other marine crustacea in the deep fresh-water lakes, Wenner and Wetter of Sweden, indicating that these basins were formerly filled with saltwater, and have been isolated from the sea by the elevatory movement of the Skandinavian peninsula which is still going on. That the same thing has occurred to our own lakes is shown by the occurrence in their depths of the genus Mysis, notwithstanding the non-occurrence of marine shells in the quaternary deposits on their shores. Kingston on Lake Ontario, is, I believe, the highest point in the valley at which such shells have been found. Very probably, at the time when the sea had access to these basins, the communication was somewhat narrow and deep, and the influx of fresh-water from the surrounding country was sufficient to occupy entirely the upper stratum, while the heavier seawater remained at the bottom. After the basins had become separated from the ocean by the rise of the land, the bottom

water must have become fresh by diffusion very slowly to allow of the gradual adaptation of the crustaceans to the change of element. Possibly the occurrence at the bottom of salt springs like those of the adjacent shores of Michigan may have had something to do with the slowness of the change. At present the bottom water, judging from a specimen we obtained from a depth of fifty fathoms approximately, is entirely fresh.

I am informed by Professor Gill that the Triglopsis Thompsonii of Girard is a marine rather than a fresh-water form. This fish inhabits the depths of the lakes, having been found by Professor Baird in the stomach of Lota maculosa, taken in Lake Ontario, and recently by Dr. Hoy in those of trout caught off Racine.

Our Mysis is allied to certain arctic forms, which would lead us to refer its original entry into the lakes to the cold period of the quaternary epoch. While the marine species usually live near the surface of the water, this one appears to be confined to the bottom, a result of its seeking the colder and at a former period the more saline waters.

The investigation of the materials obtained by the dredging parties of the Academy is now in progress, and the results will be published in full with illustrations at an early period.

CLIMBING PLANTS.

BY PROF. W. J. BEAL.

THE following remarks upon this interesting subject, can scarcely be called a review, but more properly a summary given nearly in the words of the author. It has been made

* On the Movements and Habits of Climbing Plants. By Charles Darwin, Esq., F.R.S., F.L.S., etc. [From the Journal of the Linnæan Society.] pp. 118. London, 1865.

quite full, as it is likely the original paper has been read by but few readers of the NAturalist.

Climbing plants may be divided into those which spirally twine round a support; those which ascend by the movement of the foot-stalks or tips of their leaves; those which ascend by true tendrils; those which are furnished with hooks, and those which are furnished with rootlets. The last two exhibit no special movements and are of less interest than the first three.

Spirally Twining Plants.-I begin with a special case, one depending upon my own observation, similar to the one taken by Mr. Darwin. A thrifty hop-vine in my yard went up nine or ten feet to the top of a stake. Still aspiring it ran above the support, at the same time reaching off and swinging round and round following the course of the sun. When about two feet above the stake the tip of the vine circumscribed a circle two feet in diameter. While it grew longer the extent of the circle was about the same, as a part of the vine had become strong and remained nearly stationary. By observations made at different times in the day it was found to perform one revolution in from one to two hours, moving most rapidly in the warmest part of the warmest days. It is now four feet and two inches above any artificial support, and has just tipped over to the north-east in the direction of the prevailing wind. The revolving movement lasts as long as the plant continues to grow, but each separate joint or internode, as it grows old, ceases to move. In the case of the hop and most other twining plants, about three internodes at a time partake of the motion.

The Hoya carnosa (Asclepiadacea) revolves opposite to the sun in five or six hours, making a circle of over five feet in diameter. The tip traced thirty-two inches per hour.

It was an interesting spectacle to watch the long shoot sweeping night and day this grand circle in search of some object round which to twine. Sometimes it described nar

row ellipses. After performing thirty-seven revolutions the stem of a hop was found to be twisted three times round its own axis in the direction of the sun. To prove that the twisting of the stem does not cause the revolutions, as Hugo von Mohl supposed, some stems are not regularly twisted and others twist in an opposite direction to the revolving plant. In many twining plants the end of the shoot is hooked so as the more readily to hold fast to any object of support which may be caught. This support once found, the point of contact ceases to move, but the tip continues to twine above and around the support as a rope swung around a stick will coil in the direction of the swinging rope.

If a stick shortly after having been wound round be withdrawn, the shoot retains for a time its spiral form, then straightens itself and again begins to revolve. Mohl believed that plants twined because of a dull irritability of the stem, but experiments prove that this is not generally the

case.

If the support of a twiner be not lofty it falls to the ground, and resting there the extremity rises again. Sometimes several flexible shoots twine together into a cable and thus support each other. Single thin shoots will fall and turn abruptly back and wind upwards on themselves. The majority of twiners move in a course opposed to that of the sun or the hands of a watch. Rarely plants of the same order twine in opposite directions, but no instance is known of two species of the same genus twining in opposite directions. Of seventeen plants of Loasa aurantiaca, eight revolved in opposition to the sun and ascended from left to right, five followed the sun and ascended from right to left, and four revolved and twined first in one direction, and then reversed their course. One of these four plants made seven spiral turns from right to left, and five turns from left to right. Climbers of the temperate zone will not generally twine around thick trees, while those of the tropics can. Unless this were the case those of the tropics could hardly