Protocerebral neurosecretory cells and cerebral gland

Holmgren (1916) described the cerebral gland of centipedes calling it the frontal organ. Fahlander (1938) realised that it was endocrine in nature and proposed for it the name cerebral gland. Gabe (1952) showed that axons from a group of lateral neurosecretory cells on each side of the protocerebrum carried secretory material to the cerebral glands. This was confirmed by Palm (1955).

In Lithobius forficatus the cerebral gland appears to be a hollow sac which is bathed by a stream of haemolymph and innervated by a nerve from the optic stalk, also receiving a pair of nerves originating from lateral neurosecretory cells in the protocerebrum (Palm, 1955) (Fig. 105a). The lateral neurosecretory cells are of two types, large and small, the former being far more numerous than the latter. In addition to these lateral cells there is a group of small neurosecretory cells in the posterior median region of the protocerebrum which corresponds to the pars intercerebralis of insects (Scheffel, 1961) (Fig. 105a). The nerve from the optic nerve to the cerebral gland in L. forficatus runs from the optic lobe to the gland in Lithobius calcaratus C. L. Koch. The nerve is absent in geophilomorphs and scolopendromorphs (Joly & Descamps, 1970). The large lateral neurosecretory cells (Type 1) are phloxinophil after Gomori staining, the smaller cells (Type 2) stain with haematoxylin.