Cobalt sulphide staining of optic fibres in the brain of the cricket, Gryllus campestris.

Neuronal projections from one optic lobe to other parts of the brain were stained in the cricket Gryllus campestris using the cobalt sulphide technique and Timm's sulphide-silver method. The results are: Four tracts directly connect the medulla with the lobula and medulla of the contralateral optic lobe. Direct medullar projections end mainly in the non-glomerular neuropile of the protocerebrum, but also penetrate the calyx of the mushroom bodies, pons and central body in small numbers. A few somata which send fibres into the medulla lie in the pars intercerebralis, in the protocerebrum ventral to the opposite beta-lobe, the outer margin of the medulla of the contralateral optic lobe and between deuto- and tritocerebrum. The anatomical and physiological relevance of the stained connections is discussed.