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muscles relax (Pl. 1, fig. 5). While the sea-clam lies buried in the mud, head downward, with but little power of locomotion, the fresh-water clam has the faculty of moving through the mud or sand in which it lies partially embedded. Fig. 6, plate 1, represents the natural attitude of the Unio, or fresh-water clam. It will be seen that the tubes are above the level of the sand. The foot is very large, and with it the Unio is enabled to move along slowly, the shell wedging its way through the sand, leaving a groove or furrow along the river bottom, and often the collector takes advantage of these tracks in finding them..
But little is known regarding the development of the seaclam, or Mya, as it is technically termed, but it is similar to that of the Unio. In these the eggs issue from the ovaries, and find their way into the cavities of the outer gills. There they develop until they are furnished with a little triangular shell, large enough to be recognized by the unassisted eye. At this stage they are discharged by thousands into the water, and are left to take care of themselves. It has been ascertained that they attach themselves by a little thread to the river bottom, thus preventing them from being swept away, though it is probable that not one in a hundred ever reaches maturity, as fishes and other aquatic animals feed upon them. Fig. 8, plate 1, represents the shell of the young Unio.
Many of the common fresh-water clams produce pearls, though the black mussel, with a white pearly interior, oftentimes produces pearls of considerable clearness. These pearls are caused by particles of sand or other irritating substance getting in between the mantle and shell. This irritates the animal, and this irritation causes the animal to deposit upon the particle layer after layer of pearl. In China, the natives taking advantage of their knowledge of the way in which pearls are formed, have shown their ingenuity by making flat lead castings of their little idols. These they insert in a species of fresh-water clam, by first wedging the shells
apart, and then slipping the idols in between the mantle and the shell. After a lapse of time they collect the shells and open them, and adhering to the interior of the shells they find the little lead images coated with a layer of pearl; these are neatly cut out from the shell, and are worn as charms.
It is a matter of wonder that some enterprising Yankee has not had recourse to this, as a novel mode in getting up shirt studs and sleeve buttons.
All these shells. increase in size by depositing lime around the margin of the shells, and the concentric lines upon the outside of these shells indicate successive periods of growth
For additional information regarding another species of bivalve, the salt-water mussel, the reader is referred to Vol. II, p. 243, of this Magazine.
EXPLANATION OF PLATE I.
Fig. 1. Sea-clam, Mya arenaria, with the left valve removed. H, heart,
I, intestine; G, gills; P, palpi; M, mouth; AN, anterior transverse muscle, technically anterior adductor. Po, posterior adductor; F, foot; o, opening in the mantle for foot; v, vent. This figure represents the clam with its back uppermost, and
the anterior end turned to the left. Fig. 2. Sea-clam in its natural position in the mud, head downward,
showing the tubes extended to the surface of the mud. Fig. 3. Ideal transverse section of fresh-water clam, Unio. I, intestine;
F, foot; v, ventricle; A, auricle; G, gills; M, mantle; s, shell. Fig. 4. Transverse section of Mya, showing the position of the spring to
open the shell. M, muscle; L, ligament. Fig. 5. Transverse section of Unio, showing the position of the spring to
open the shell. M, muscle; 1, ligament. Fig. 6. Fresh-water clam, Unio complanatus, in its natural position, crawl
ing. The anterior end is depressed, and the foot is seen
thrust out ahead. Fig. 7. Heart of clam seen from above. v, ventricle; A A, auricle; G G, line
of gills. Fig. 8. Young of Unio.
THE SENSES OF SIGHT AND SMELL OF THE WILD
TURKEY AND THE COMMON DEER.
It is claimed for the wild turkey that it has the quickest and most accurate sight of any known animal. It is a saying among old hunters that it can detect the human eye looking through a knot-hole from the inside of a hollow tree. I once observed an incident illustrative of its remarkable power of sight, and tending to show that its apprehension of scent is correspondingly dull.
In December, 1847, I was hunting deer on the Vermilion River, and had been following one from daylight till three o'clock in the afternoon, over the breaks and bluffs of the Vermilion River, through six inches of dry hard snow, almost as difficult to walk in as dry corn-meal.
When near the foot of the bluff, not far below the mouth of Deer Park, some distance off, I saw a flock of wild turkeys crossing the river on the ice, and coming directly towards me. My ambition immediately fell from a deer to a turkey. I concealed myself in a very dense thicket of underbrush, and soon heard the turkeys approaching with that contented quit, quit, in which they frequently give expression to a happy sense of security. My pointer, which was as good at following a deer as a grouse, stood at my feet without moving a muscle, though his eyes shone like balls of fire when he scented the turkeys and heard them pass by. They passed, I should judge by the noise, not more than fifty or sixty feet from me, without taking the least alarm. About fifty yards distant there was a bare spot of considerable extent, near the brow of the bluff to which their course would evidently take them, where I promised myself a sure shot. I rested my gun against a small tree that I might make no perceptible motion before