. ABC Fig. 2. Ceratias holbolli Kroyer. The caruncles. A, 'Mancalias tentaculatus', x 5. B, Antarctic specimen, x z\. C, Regan's specimen, x it. In Regan's specimen the cephalic tentacle is absent and he notes ' that the dorsal tentacle is long, reaching beyond the base of the caudal fin, when laid back, and bears a terminal bulb' (Regan, 1926, p. 34). He considered this was either the normal structure of the dorsal ray, or an assumption of the structure and function of the cephalic tentacle caused by loss of this tentacle during life (Regan, 19250). I have re-examined this long dorsal ray, wh
. ABC Fig. 2. Ceratias holbolli Kroyer. The caruncles. A, 'Mancalias tentaculatus', x 5. B, Antarctic specimen, x z\. C, Regan's specimen, x it. In Regan's specimen the cephalic tentacle is absent and he notes ' that the dorsal tentacle is long, reaching beyond the base of the caudal fin, when laid back, and bears a terminal bulb' (Regan, 1926, p. 34). He considered this was either the normal structure of the dorsal ray, or an assumption of the structure and function of the cephalic tentacle caused by loss of this tentacle during life (Regan, 19250). I have re-examined this long dorsal ray, which emerges from the torn base of the former integument of the tentacle (Fig. 2C). It is spirit material, and appears inelastic and much shrivelled. Probably it represents a part of the pterigiophor prolonged by remnants of its musculature; the ' terminal bulb' seems to be a bunched knob of connective tissues. There is little doubt that these damaged structures correspond to the dorsal tentacle of the Antarctic specimen. The musculature of the cephalic tentacle of the Ceratioids has been studied in Gigantactis by Brauer (1908) and Waterman (1948), and in Ceratias by Rauther (1941) and Bertelsen (1943). Brauer could find only four pairs of muscles associated with the structure. Both Bertelsen and Waterman have recorded five pairs, which can be homologised in the two genera. Two of these muscles are the retractors and exsertors of the basal bone. They are elongate and weak in Gigantactis where fore-and-aft adjust- ability of the lure is not specially developed. On the other hand, in Ceratias they are elongate, but also large and powerful, and are the principal effectors of the mechanism already described. A third pair of muscles are attached to the basal bone. They are powerful in Gigantactis, where Waterman describes them as the inclinators of the illicium. They are small and weak in Ceratias, where they may also, as * By the ship's surgeon, Dr Michael Gilkes, to whom I am indeb
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