JMiscellanies. yi 
**T have in vain attempted to satisfy myself as to the nature of their 
food. Dissatisfied with the results of the observations mentioned in 
volume third, I procured, among other species, a fine Unio cariosus, - 
the valves of which were much more gaping than usual. Selected 
specimens of various species were placed in a glass vase, in the bot- 
tom of which was placed clean white sand, so that their natural beds 
might be somewhat imitated. In this vessel they assumed their natu- 
ral position by pushing the sand behind them with the protruded foot, 
thus forming a pit into which the base of the shell gradually fell, the 
ligament taking the most elevated situation. In this position, they 
soon began to travel round the vessel, and this locomotion continued 
for some days, when it ceased entirely. 
“Their extreme timidity or apprehension on the approach of dan- 
ger was very evident. At first, the slightest agitation, or movement 
of the vessel caused them to close their valves instantly. Being 
almost daily disturbed, this alarm after a time ceased, particularly with 
my fine cariosus, which now suffered even the agitation of the water 
without closing the valves, stretching out its fine dark and beautiful 
tentacula from the borders of its mantle, and forming by the contact 
of its edges, two openings, one below the other. 
‘“‘From the superior of these openings, the constant stream ejected 
could be plainly perceived for two inches, elevating the water at its 
surface. Being very anxious to ascertain through what part the water 
necessary to supply this stream was carried into the shell, I discover- 
ed it, after many experiments, to pass in by the inferior opening; that 
it passed out by the superior one had always been evident. This op- 
eration was unremitted while the water was fresh; when left un- 
changed for some days, this current invariably ceased. Doubting the 
correctness of my former idea, as to the probability of their feeding 
on animalcula, from the circumstance of finding the passage of the 
water to exist only while fresh, and never when animalcula were visi- 
ble even with a microscope of great power, I instituted some experi- 
ments by passing pieces of bread, very small pieces of worms, &c. 
between the tentacula. Several of them would sometimes remain for 
some minutes within the mantle, and so far within as to be invisible, 
but they were in every case in a very short time thrown out witha 
rapid and sudden jet of water to the opposite side of the vessel. 
“These experiments were frequently repeated during the course of 
a year upon the same specimen, and the result was uniformly the same. 
No food introduced into the shell could be ascertained to have remain- 
ed; it may therefore be pretty safely concluded, that neither animal- 
cula, nor food in a more solid state are necessary to the nourishment 
of the Naiades. What then are we to conclude it to be? would the 
Vou. XXII.—No. 1. 23 
