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Mathews, A. P. '99 The metabolism of the pancreas cell. Journ. of Morphol., Vol.

XV, Suppl. Montgomery, T. H.

'98 Comparative cytological studies with special regard to the morph

ology of the nucleolus. Journ. of Morphol., Vol XV, No. 2. Nelis, Charles.

"Oo L'apparition du centrosom dans les cellules nerveuses au cours de

l'infection rabique. Nevraxe, Vol. I. Pugnat, C.

'98 Des modifications histologiques de la cellule nerveuse dans ses divers

états fonctionnels. Bibliographie anatomique, T. VI. Rohde, E. '95 Ganglionzellkern, Achsencylinder und Punktsubstanz. Arch. f.

mikr. Anat. '96 Ganglionzellkern und Neuroglia. Ein Kapital über Vermehrung

u. Wachsthum von Ganglienzellen. Arch. mikr. Anat. '98 Ganglienzelle. Zeitsch. Wiss. Zool. '03 Untersuchungen über den Bau der Zelle. 1. Kero und Kernkorper

Zeitsch. Wiss. Zool., Vol. LXXIII. Scott, F. H.

'98-'99 The structure, micro-chemistry and development of nerve cells

with special reference to their nuclein compounds. Transactions of

Canadian Institute, Vol. VI. Sjövall, E.

'03 Die Nervenzellen veränderungen bei Tetanus und ihre Bedeutung.

Jahrb. f. Psychiatrie und Neurologie. Verworn, N.

'99 General physiology. English translation, The Macmillan Co.

EXPLANATION OF THE FIGURES. The following figures are free-hand drawings using Zeiss Oc. 4+Obj. 1.12.

a, centrosome ; b, amoeboid processes ;,<, basophile granules ; d, acidophile granules; e, accessory nucleolus.

Fig. I to Fig. 6, Spinal ganglion cells of foetal white rat.
Fig. 7 and Fig. 8, Celis in ventral horn of adult white rat.

PLATE III.

Fig. 1, Stained with Biondi-Ehrlich's tricolor.
Fig. 2, Treated with MacALLUM's technique which shows the distribu-

tion of iron.

Fig. 3, Stained with Biondi-Ehrlich's tricolor.
Fig. 4, Stained with HEIDENHAIN's iron-haematoxylin.

PLATE IV.

Fig. 5, Stained with BIONDI-EHRLICH's tricolor.
Fig. 6, Stained with Biondi-EHRLICH's tricolor.

Fig. 7, Treated with MACALLUM's technique which shows the distribution of phosphorus.

Fig. 8, Stained with Haidenhain's iron-haematoxylin.

AN ESTABLISHMENT OF ASSOCIATION IN HERMIT

CRABS, EUPAGURUS LONGICARPUS.

By E. G. SPAULDING, Ph. D. (Bonn).

College of the City of New York.

Introductory. The experiments described in this paper are the result, first, of preliminary observations of a number of hermit crabs kept for some time in an aquarium at the Woods Hole Laboratory, which showed them to be quite capable of profiting by experience. In fact, the results first obtained were in general quite confirmatory of those obtained by the subsequent more systematic investigation, the method for which they indicated.

Bethe’ and YERKES’ have each made experimental studies of habit formation in the Crustacea, the former on the crab, Carcinus moenas, the latter on the crawfish, Cambarus affinis, and on the green crab, Carcinus granulatus. Bethe at the end of his paper relates some experiments made to determine whether or not the crab possesses psychical processes, with the result that he asserts that it does not. This conclusion is not, however, necessarily to be accepted even from Bethe's own experiments, for the reason that these at best serve to demonstrate the absence of only one kind of psychical phenomena, viz., those of inhibition or control; other kinds may be present.

BETHE himself does not recognize that the method he employed was defective in this respect, but an account of it will, we think,

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" BETHE, A., Das Centralnervensystem von Carcinus moenas. Archiv f. mikr. Anat, Bd. 51, 1898.

Yerkes, Robert M. and HUGGINS, GURRY E. Habit Formation in the Crawfish, Cambarus affinis. Harvard Psychological Studies, Vol. I. 1903.

YERKES, Robert M. Habit Formation in the Green Crab, Carcinus granulatus. Biolog. Bulletin, Vol. III. 1902.

make evident the justification of our criticism. His first experiment was to place a crab in a basin in the darkest corner of which there was an Eledone (a cephalopod). The crabs, because of their instinct to hide, moved immediately into this corner and were seized by the Eledone. Freed from its grasp one crab returned repeatedly five times, another six, to the dark and the enemy, showing, as BETHE thinks, that it had not profited by experience. It is to be emphasized, however, that to have done this latter in the way Bethe thought possible, it would have been necessary that the crab inhibit its instinctive action. This inhibition could take place only if, first, a representation of the pain of the seizure by the Eledone were present, and second (and essentially), if the representation were the "stronger”?; the other possibility, that the representation should occur and yet be overcome by the instinct, is accordingly not disproved by Bethe's experiment. The same criticism applies also to his second method that, notwithstanding maltreatment on each such occasion, the crabs repeatedly seize food when offered

The criticism above made is quite in agreement with that principle of method for comparative psychology which is in reality very simple, but not always observed, that in any instance where the question of the presence of consciousness in any species is admittedly to be decided by experimentation, this question must take a particular form, and our efforts must be directed to the establishment of the presence or absence of some definite kind of consciousness, e. g., associative memory between constructs of two sense fields, conceptual reasoning, etc.

YERKES in his experiments with the crawfish made use of the labyrinth method. The subject could escape from a box into the aquarium only by "choice of a certain passage.” The "choice" consisted in or was manifested by learning (by repeated experience) to avoid the blocked passage and gain the aquarium by the most direct path. Accordingly all conflict, requiring inhibition, between the two elements or “constructs" to be associated, viz., "correct path” and “aquarium,” was ab

sent. “Correct path,” as opposed to the incorrect, logically implies in these experiments “aquarium"; and its selection, as shown by the ratio of improvement from day to day may, though not necessarily, imply the representation of the construct "aquarium," but it does demand the admission that acts of recognition and discrimination, or even of what Lloyd MORGAN calls “perceptional inference” take place. These in turn presuppose necessarily, as is well known, retention and production.

Carefully excluding the possibility of the crab's merely following a path by smell, taste, or touch (although if it did only this one could not account for a correct after an incorrect choice had once been made) YERKES found in one case that after 40, in another that after 250, experiences no mistakes in choosing were made. In a number of cases the subject turned from, before it reached, the partition which blocked the passage, thus showing the important part played by vision in direct ing the animal in the absence of smell, taste, and touch. All of these, however, together with muscular sensations, YERKES concludes normally play a part in the formation of labyrinth habits. These experiments therefore seem to show that upon the basis of the constructs” which one sense alone, viz., vision, give the crab, a consistent selection of the correct path is possible ; but this is explainable it seems, even if it is considered that only a recognition of each successive part of that path and consequently a discrimination between it and the incorrect is made, and yet that no representation or "reconstruction" of "aquarium" takes place, although of course this latter interpretation is not excluded.

A method of experimentation, however, which shows that in the formation of a habit, or in the learning of a motor reaction involving two sense fields, e. g., taste and vision, it is necessary to overcome an instinct or tropism in the opposite direction, such a method, we think, would at least give more cogent grounds for accepting the presence of representation than one not doing this, although even here conservatism in making this claim would be the safer course.

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