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Show 1905.] BEARING ACTINIANS IN THEIR CLAWS. 5 0 5 actinians remained altogether passive without even retracting ; sometimes the points of the maxillipeds would penetrate the delicate flesh of the polyps and be freed only after a struggle. By far the most unique and remarkable reactions were those observed when the actinians were supplied with food. When shreds of meat were placed on the disc of the polyp, the latter responded in the usual manner of actinians by bending its tentacles towards the disc and partly closing over the food. If the pieces were too large to be wholly covered and readily ingested, the crab seemed to be soon aware of their presence, and would then bring forward the hook of one of the first ambulatory limbs and apply it to the oral disc from time to time until all the fragments of food were removed and transferred to its own mouth. Thus the freshly broken chela of a small Alphceus was placed upon the oral disc of the actinian so carefully as not to touch any part of the Melia. Immediately the polypal tentacles closed over it preparatory to ingestion, but before the process was accomplished the first ambulatory limb of the crab reached over among the tentacles and dragged away the fragments to its own mouth. If the fragment were sufficiently small as to rest wholly on the disc of the polyp, and the latter quickly opened its mouth to swallow it, the Melia might then exhibit no responses and the actinian appropriated the food. But in very few instances in a number of feeding experiments were the ingestion reactions of the actinian sufficiently rapid as to wholly indraw the food before the crab would extend an ambulatory limb and vigorously abstract it. In some instances the fragments were already partly swallowed by the polyp when the crab, receiving some stimulus, would extend an ambulatory limb to the polypal disc, and actually abstract the food from the stomodasum of the actinian and transfer it to its own mouth. The feeding experiments loere sufficient to demonstrate beyond all question that Melia actually takes away and appropriates to itself the food procured by the actinian. In the language applied to human actions, it can be truly said that the crab robs the actinian of its food, though no one would think of introducing ethical considerations into the act, even if consciousness could be established. What are the means by which the crab is made aware of the presence of food-material on the disc of the actinian, or, rather, what determines the very definite responses of the clielipeds towards the disc of the actinians ? It is certainly not a tactile reaction, for the responses took place when the food-particles could not possibly have come into contact with the crab or any of its tactile organs. It may have been that the movements of the polyp during ingestion produced some stimulus which was transmitted through the clielipeds, but ordinary stimulation of the actinian by mechanical means failed to call forth any responses on the part of the crab. It is most probable that the reaction is 34* |