. Cephalopoda. Cephalopoda. The cirrus can be greatly extended and shortened; it can be retracted almost completely into the sheath or project in its greater part. This specialization of the arm base into a sheath is specific for Nau- tilus. The Dibranchiata show no trace of it, which suggests that sheaths were absent in the common ancestors of these groups (Chapter 1). By growing together into complexes of various size, the sheaths make mor- phological orientation within the arm crown extremely difficult. In these complexes only the distal end with the cirrus opening remains free; the true ar
. Cephalopoda. Cephalopoda. The cirrus can be greatly extended and shortened; it can be retracted almost completely into the sheath or project in its greater part. This specialization of the arm base into a sheath is specific for Nau- tilus. The Dibranchiata show no trace of it, which suggests that sheaths were absent in the common ancestors of these groups (Chapter 1). By growing together into complexes of various size, the sheaths make mor- phological orientation within the arm crown extremely difficult. In these complexes only the distal end with the cirrus opening remains free; the true arm base, including the base of the cirrus, remains concealed. Never- theless, the following may be recognized (Figure 12, p. 65). (63). FIGURE 11. Cirri of N a util us pompilius: a — cirrus of the outer series of arms (grasping arms) (Vg natural size); a^ — same,highly mag- nified in profile; a2 —transition between the inner and outer surface; 33 — profile of the proximal part; — cross section through the distal part; b - sensory cirrus (*/^ natural size), inner and lateral aspect, comblike; bj — cross section; c — ophthalmic cirrus (apex) (V3 natural size); c^ — cross section. The cross sections show adhesive pads on the arms within which the oval cross section of the nerve is visible, and the artery and the vein (black) below. Note the variable form of the adhesive pads. 59. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Naef, Adolf. Jerusalem : Israel Program for Scientific Translations
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Keywords: ., bookcentury1900, bookcollectionbiodivers, booksubjectcephalopoda
