. Cephalopoda. Cephalopoda. 299 and also the appearance or persistence of stalked eyes (cf. Vol. II, Plate IV). One has only to assume an invagination of the skin into the transparent gelatinous part of the forehead, causing the disappearance of this unnecessary tissue. The arm circle and eyes are already normally independent of each FIGURE 143. Young stage of Thelidioteu this a 1 e ss a nd r i nii. 5x. Collected on 19 January 1903 in the Naples plankton. Note the resemblance with Figure 141 and the distribution of the luminous or- gans connected with certain chromatophores on head,man
. Cephalopoda. Cephalopoda. 299 and also the appearance or persistence of stalked eyes (cf. Vol. II, Plate IV). One has only to assume an invagination of the skin into the transparent gelatinous part of the forehead, causing the disappearance of this unnecessary tissue. The arm circle and eyes are already normally independent of each FIGURE 143. Young stage of Thelidioteu this a 1 e ss a nd r i nii. 5x. Collected on 19 January 1903 in the Naples plankton. Note the resemblance with Figure 141 and the distribution of the luminous or- gans connected with certain chromatophores on head,mantle and ten- tacles, the form of the forehead (at 3) and the head as a whole. 1 — Luminous organ of the tentacle stalk; 2 — same, visible through the protective membrane at the base; 3 - gelatinous mass of "forehead" 4 — indication of the tentacle pockets. (Cf. also Figure 88.) The general appearance is that of a typical larva of Enoploteuthidae. The relationships between mantle and shell are as in Figure 140, i. e. not only the rhachis but also a large part of the flag (lanceola) is free of the muscular mantle. The fins are connected only at the posterior end by a straight, transverse edge. The fins are rounded, nearly circular. The 3 corners of the mantle margin are only indicated. The funnel apparatus resembles that of the young Abraliopsis. The eyes have begun their lateral displacement; the olfactory organs still retain their typical early larval form and position but are beginning to be displaced toward their position in the adult. A sinus is already recognizable on the lid margin. Particularly interesting is the arm apparatus. The second pair is still the longest; the third pair is already as long as the first but still much shorter than the second, while the fourth pair is only about half as long as the third (Formula: 2, 1 = 3,4). Apical swellings on the ventral arms are absent. All arms bear 2 rows of suckers which are much smaller on the ventral arms.
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Keywords: ., bookcentury1900, bookcollectionbiodivers, booksubjectcephalopoda
