Quarterly journal of microscopical science . d to the level of the nauplius eye and then expandsdorsally into the bay from which arises the second antenna,. In the living animal the labral glands can be seen indistinctlyin the anterior part of the labrum and are of a pale-yellowcolour, as was observed by Ley dig (12). Proximal Group.—This consists of two laterally placedgroups of epidermal cells which almost meet in the mid-ventralline between the first antennae. Each group commences justin front and close to the ganglion of the nerve to the tirsiantenna (PI. 10, fig. 13), and extends postero-
Quarterly journal of microscopical science . d to the level of the nauplius eye and then expandsdorsally into the bay from which arises the second antenna,. In the living animal the labral glands can be seen indistinctlyin the anterior part of the labrum and are of a pale-yellowcolour, as was observed by Ley dig (12). Proximal Group.—This consists of two laterally placedgroups of epidermal cells which almost meet in the mid-ventralline between the first antennae. Each group commences justin front and close to the ganglion of the nerve to the tirsiantenna (PI. 10, fig. 13), and extends postero-dorsally overa lozenge-shaped area lining the lateral cuticle of tli< labiumas far back as the labral nerve (lls. Hand 10, tigs. 1 I and 18).Bach group consistsof about twenty cells, and the nuclei of these 21G II. GRAHAM CANNON vary in size, being smallest at the base of the first antennae andlargest about the centre of the group. The nuclei are usuallyabout 20// long, but the smallest are never less than half this Text-fig. 1. curd I. Semi-diagrammatic ventral view of Simocephalua thick clotted lines ending in arrow heads on the animalsleft side indicate the direction and extent of the normal move-ment of the appendages figured on that side.) adg, anteriorpair of distal gland-cells; ant 1. first antenna; ant 2, secondantenna ; cd, connexion between anterior and posterior pairsof distal gland-cells ; en 3, proximal endite of third trunk-limb;ex 2, exopodite of second trunk-limb; , branchiae of first, second, andthird trunk-limbs respectively ; /. labium ; tndb, mandible ; ,maxilla ; pdg, posterior pair of distal gland-cells; pg, proximalgland; til, //2. // 3, first, second, and third trunk-limbsrespectively. length. For comparison it may be stated that the length ofthe nuclei of nerve-cells r of muscle-cells, which arc of very uniform size and oval shape, is 4/j. Thus the volume of theselarge gland-cell nuclei must be many limes,
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