lusks, when irritated, produce an extremely abundant secretion of mucus or "slime"—so much, indeed, as to sometimes render a small quantity of water in which the animals may be confined, quite sensibly gelatinous. He suggests that the change to fresh water may induce such a secretion of mucus, and perhaps of carbohydrates and fats as well, as would account for the increase of these substances in the liquids. The observation of oyster-dealers that "water always thickens the natural juices that adhere to the surface of the oyster and makes it slimy," accords with Professor Conn's statement.
If such secretion did take place, the flesh must probably have lost a little protein during the floating. The estimates of absolute gain and loss of weight of flesh and ingredients are based upon the assumption that the quantity of protein was unaltered in floating. If protein was given off, therefore, the estimates are wrong. But the quantity of protein secreted and the consequent error must be, at most, very slight. If there is an error, its effect would be to make the quantities of nutrients after floating appear larger than they really were. In other words, if the error were corrected, it would make the loss of nutritive material in floating greater than it appears to be in the figures above given.
The experiments might have been so conducted as to decide this question of the exact gain and loss of weight of each material in the oysters. It would have been necessary to simply take a larger number in each lot before and after floating, and be certain that the number, weight, and bulk were the same in the floated and not-floated lots of each experiment. For instance, we might, in each experiment, carefully select two lots of, say, a bushel each, as taken from the beds; have the number of oysters the same in each bushel, as an additional assurance that the two lots were alike; float one bushel, and weigh and analyze both. A few experiments of this sort made under different conditions of time, temperature, kind, and age of oysters, etc., would give very reliable and valuable data. Unfortunately, the means at my disposal did not permit so thorough experiments. I am persuaded, however, that the results of such series of trials, if they could be made—and I wish they might be—would be very similar to those of the trials here reported.
It is very interesting to note that these processes of both osmose and secretion which we have been considering in the body of the oyster are apparently very similar to processes which go on in our own bodies—namely, those by which our food, after it is digested, finds its way through the walls of the stomach and other parts of the alimentary canal into the blood, to be used for nourishment. Physiologists tell us that the passage of the digested materials through the walls of the canal is in part merely a physical action, due to osmose, but that it is in part dependent upon a special activity of the cells of the villi. In like manner, the changes in the composition of the oys-
