Food choice experiments were carried out with three species of pycnogonids:Nymphon rubrum, N. gracile, andEndeis spinosa.Running sea‐water that had circulated over different possible food‐sources (hydroids, actiniarians, octocorals, synascidians) was offered to the pycnogonids at one side of a basin, pure sea‐water or sea‐water that had flowed over a different source of food at the other.The experiments, though few in number, seemed to indicate that:(1) Pycnogonids are capable of detecting the presence or absence of various coelenterate species.(2) They are able to discriminate between different food‐sources, i.e. the nature of the chemical substances produced by the food determines the degree of attraction.(3) The preferential sequence for the three pycnogonids tested is:Nymphon rubrumprefersDynamenaoverTubulariaandLaomedea; these are preferred overActiniaandMetridium; there is no attraction toAlcyonium. Nymphon gracileprefersLaomedeaoverDynamena. Endeis spinosaprefersLaomedeaoverDynamena; these are preferred overActinia; there is no attraction toMorchellium.(4) Experimental amputation of appendages indicates a high probability that the chemo‐receptors of the pycnogonids are not located on the chelifores, palps, or ovigers. They may be located (a) all over the body, possibly in innervated epidermal bristles; and/or (b) in the distal part of the proboscis, bearing sensory setae; and/or (c) on the w