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hind the inserted screen first, and feeding in the light. From the data already obtained it would be expected that in this a greater per cent. of crabs would from the start make their exit than had in the first experiment made their entrance. This proved to be the case as the following record shows :

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Comparison of this with Experiment I shows that not until the 5th. day was as high a ratio approximately obtained. In both cases of course the crabs are guided by taste; the two experiments together, therefore, serve to demonstrate the natural preference for the light, and the quicker results obtained when this works with than when against the feeding instinct.

EXPERIMENT IV.

Lot 3.

This same preference was demonstrated by a second control experiment. Twenty-four crabs were placed in a large rectangular aquarium directly next to a window with a northeast exposure. Half of the aquarium was darkened by holding down with a stone a box with one end taken out. Sand was placed over the entire bottom.

Twenty observations failed to discover a single crab inside the “dark line" from edge to edge of the box. The crabs, therefore, seem to prefer the light to the darkness, at least in the aquarium.

EXPERIMENT V.

Lot 6. A third very similar control experiment was also confirmatory. Thirty crabs, the aquarium jar and screen exactly as in Experiment I were employed. The question might arise, would not the crabs possibly "learn" to go behind the screen when this was inserted even though no fish was there, the necessary feeding being done at other times.

Should they do this the conclusions from Experiment I would be quite

worthless. The results were that they would not enter.

Ten observations were made; in seven of these cases no crab (within 5') went further than to the edge of the entrance, which had in no experiment been counted as "in"; of the three other cases, within the period of 5 minutes, 5, 8 and 5, respectively entered, but there was no evidence of progress.

ADDITIONAL EXPERIMENTS.

Maze Experiment. Can the Hermit learn to go through a maze for its food ? A simple maze was constructed of thin boards in such a way that it was necessary for the crabs, 16 being used, to enter at one end, go through to the other, enter the second passage, go back to the other end and enter the food compartment, The crabs were first given an opportunity to “become acquainted" with the maze by leaving it in the aquarium about two hours. The next day this was repeated with the result given in the first line of the table.

The results are as follows:

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This experiment was not conducted as carefully as it would be possible to make it; the crabs could not be watched all of the time, but only occasional observations and a record, as the above, at a stated time, made. The results showed, however, though perhaps not as clearly as might be desirable, that an improvement had taken place, and they have a value, as being in general confirmatory of the first experiment.

Conclusions.

The Hermit Crab, Eupagurus longicarpns, is capable of pofiting by experience, in a rather short time, by associating the “constructs” of two “sense fields," vision and taste. The existence of this association is proved by its effectiveness in subsequently bringing about, with only one stimulus presented, the same reaction against a natural positive heliotropism, as previously occurred with two stimuli present. The reaction here is therefore conditioned internally, as well as externally. The internal condition must be identical with either the excitation of, or with that and the reproduction from the “after-effect" of the second, the “taste-stimulus ;" if there is only excitation then the internal event is only physiological ; if there is also reproduction then it is psychical as well as physiological.

Both interpretations agree equally well with the data obtained, for the reason that even in the second case there must be a physiological basis for the psychical events if present, and consequently, the two being quite compatible as ultimately regular and uniform series of events, there is theoretically no certain objective criterion for the presence here of consciousness.

Practically there is, however, such an objective criterion which we make use of in our intercourse with other men, and if the above data are interpreted in as strict analogy to this as possible, it seems justified to consider that the Hermit Crab "reproduces" or, if one will, remembers vaguely.

The author, as a holder of one of its research rooms” at Woods Hole wishes to acknowledge his indebtedness to the Carnegie Institution for the opportunities thus presented for the carrying on of this and other investigations.

Jan. 12, 1904.

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EDITORIAL.

L'ENVOI.

The change recently announced and, by the appearance of this number, placed in process of realization means much to the writer. It means, among other things, the fulfillment of a cherished desire and the realization of hopes which led to the founding of the Journal of Comparative Neurology at a time when the prospect of either scientific or material support seemed very small. The small but growing band of investigators in this country were much better than their promise in supplying material and in supporting the enterprise from the start. In spite of the fact that the specific purpose of the venture was realized only in part, a fact partly to be accounted for by the long-continued incapacity of the writer, it is believed that the thirteen years of the existence of the Journal have not been entirely unfruitful.

It seems not inappropriate that the writer should avail himself of this occasion, apparently so full of promise for greater usefulness in the future, to express his personal gratitude for the unselfish toil which has been expended by the numerous collaborators on the staff during a period of nearly ten years, during which care on his part has been impossible and his own responsibility of the most perfunctory kind. To my brother, Professor C. JUDSON HERRICK, especially, who has carried the administrative and editorial responsibility, much of the time with little or no assistance, and on whom the financial burden has too largely fallen, the Journal owes its continued existence and the new lease of life to which we now look hopefully forward. Thanks are due also to the many others, both in this country and abroad, who have actively shared in the responsibilities and have contributed from their original material, as well as to the numerous friends who at this emergency have contributed money to enable us to enlarge at once, pending the substantial increase in circulation which is already in progress.

At the time the earlier numbers were issued there was little of that camaraderie and acquaintance among the widely scattered workers in this, as in many other lines, which now is one of the pleasant and encouraging features of scientific work. With a growth of this fellowship we note with gratification the almost entire disappearance of the acrid or acrimonious criticism that disfigured early scientific literature in America. It is now possible to admit differences of opinion or to detect errors in the work of another without establishing forth with a breach of cordial relations among the workers. C. L. HERRICK.

Structure and function are correlative concepts; neither is complete without the other; as cause implies effect, so function implies structure. These are trite statements, yet it would seem that we can not be reminded too often that the understanding of life is dependent upon our ability to correlate structural and functional facts. It is chiefly in the interest of such correlation that The Journal of Comparative Neurology and Psychology is published. True, there is no more reason for considing the psychic process a function of the nervous system, than for calling the brain a function of consciousness; but, this aside, animal behavior and the functions of the sense organs and central nervous system are dependent upon neural structures, and it is these which most concern us. A survey of modern research literature shows clearly that those investigators have been eminently successful who have studied structure and function at the same time. To the physiology of the senses vastly more is contributed by those who know form as well as function, than by those who neglect anatomical conditions ; in animal behavior, it is from the student who attends to anatomical and histological facts that a satisfactory account of the reactions of an organism is to be expected.

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