Eyestalks of cavernicolous Troglocaris sp. cf. anophthalmus from an Istrian cave were examined by light- , scanning- and transmission electron microscopy. Apart from nervous tissue inside the eyestalk, no indications of ommatidia or their constituent cells tvere found. A few sensory bristles on the outer surface and piles of conderLSed membrane, surrounded by what could have been haemocyte spherules, in the cvtoplasm of sub-cuticular eyestalk cells were seen instead. Electrophysiologically and behaviourally no sensitivity could be demonstrated.