. Text-fig. 27. Ascidia challengeri Herdman (St. 145): Oral tentacles. External appearance. The specimens range in length from 1-3 cm. to n-o cm., the largest being from the Ross Sea. They vary from a regular oval and laterally flattened form to an irregular pear- shaped form. The siphons are generally, but not always, inconspicuous, the oral one terminal and the atrial about one-third of the body length from it. No. of tentacles Dorsal lamina No. of longitudinal branchial bars per side Intermediate branchial papillae Branchial stigmata Table 27 A. dispar About 50 Extends far beyond oesop
. Text-fig. 27. Ascidia challengeri Herdman (St. 145): Oral tentacles. External appearance. The specimens range in length from 1-3 cm. to n-o cm., the largest being from the Ross Sea. They vary from a regular oval and laterally flattened form to an irregular pear- shaped form. The siphons are generally, but not always, inconspicuous, the oral one terminal and the atrial about one-third of the body length from it. No. of tentacles Dorsal lamina No. of longitudinal branchial bars per side Intermediate branchial papillae Branchial stigmata Table 27 A. dispar About 50 Extends far beyond oesophageal mouth 40-50 Absent Short and irregular A. challengeri Few, usually up to 20 Scarcely extends beyond oesophageal mouth 30-32 Usually present Long and regular Remarks. Arnback (1938) described a new species A. dispar, based on a single specimen from South Georgia. She recognized the strong similarity to A. challengeri, but gave as main distinctions those shown in Table 27. Of these characters the ones which, judging by distinctions between other species of Ascidia, are likely to be the most reliable are (1) the number of tentacles, (2) the number of longitudinal branchial
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