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Show 134 ON THE ANATOMY OF GONATUS FABRICII. [Mar. 5, this. The presence of a phragmocone, the absence of the nuchal muscle, the form of the median tooth of the radula, and the presence of nidamental glands are all points of considerable importance, whilst the size of the anterior salivary glands is merely a matter of degree, and the form of the anal appendages in the adult Gonatus is unknown. The fusion of the median retractors in one is, so to speak, balanced by their separation from the lateral retractors in the other. The other remaining point, namely the opening of the oviducts into special cavities in Onychoteuthis, does not seem sufficient in itself to contravene the resemblances on the other side. Summary. In addition to the general sketch of the anatomy of an interesting form, the preceding pages record the existence of several tracts of cartilage hitherto unobserved in the Cephalopoda, and give details regarding the structure of the pen-sac and the development of the pen, as well as new facts regarding the structure of the funnel-organ. The genus Gonatus is regarded as being somewhat more nearly related to Onychoteuthis than to Enoploteuthis, but as much further removed from both than they are from each other. The creation of the subfamily Gonatidce is held to be justified. In conclusion, I have lo fulfil the pleasant duty of thanking Mr. Robert Gray for some of my materials, Professor Huxley for his kindness in allowing m e the use of his workroom, and Professor G. B. Howes for the friendly interest he has taken in my work and for numerous acts of kindness during its performance. EXPLANATION OF THE PLATES. These letters have the same signification throughout. a. Anus. op' a.ao. Anterior aorta. br. Gills. br.a. Branchial artery. br.h. Branchial heart. br.h'., br.h". Branchial hearts. b.g. Buccal ganglia. br.g. Branchial ganglia. br.v. Branchial vein. c. Csecum. ce. Cerebral ganglia. co.', co". Inner and outer limbs of the collaris muscle. cp. Plug of cartilage in the hinder extremity of the pen-sac. d.g. Digestive gland. c', e". Epithelium of the pen-sac. em. Epithelium of the mantle. g. Articular groove on siphon. i.s. Ink-sac. m.m. Retractores infundibuli. nu. Nuchal cartilage. od. Oviduct. ce. Oesophagus. op. Optic ganglia. the Their stem cut short. osp. Foramen for the nerve to the osphradium. o. v. Vein probably from the ovary. p. Pen. pall.v. Pallial vein. pan. " Pancreas." p.ao. Posterior aorta. p.gl. Pericardial gland. p.n. Pallial nerve. p.v. Pedo-visceral ganglia. p.v.c. Posterior vena cava. r. Rectum. re. Renal sacculi on the veins. ri. Ridge for pallio-siphonal articulation. s. Stomach. sep. Rudimentary septum of the phragmocone. s.g. Stellate ganglia. s.nu. Supra-nuchal cartilage. su.g. Supra-gladial cartilages. v. Ventricle. v.c. Vena cava. v-f-, v.f. Venous foramina in the cephalic cartilage. |