- Externally in all species a layer of ciliated cells forms the outer investment.
These posterior brain-lobes, which in all Heteronemertines are in direct continuity of tissue with the upper pair of principal lobes, cease to have this intimate connexion in the Metanemertini; and, although still constituted of (I) a ciliated duct, opening out externally, (2) nervous tissue surrounding it, and (3) histological elements distinctly different from the nervous, and most probably directly derived from the oesophageal outgrowths, they are nevertheless here no longer constantly situated behind the upper brain-lobes and directly connected with them, but are found sometimes behind, sometimes beside and sometimes before the brain-lobes.
Externally uneventful as his life henceforth necessarily was, it was marked chiefly by the reception of distinguished personages and of numerous pilgrimages, often on a large scale, from all parts of the world, and by the issue of encyclical letters.
- Externally, sulphur is of use in skin affections.
These glands are represented externally by a special plate, the cribellum, which lies in front of the ordinary spinning mamillae, and by a comb of short bristles, the calamistrum, placed in the penultimate segment of the left of the last pair.