Postscript. 296 Tilis paper was read in „Dansk Naturhistorisk Forening". On this occasion Prof. A. Krogh suggested that the gills in Mola and Xiphins might possibly be used for air-breathing. I thought over the matter and read, what is written of the hfe- habits of these fishes. About Xiphias it is told that it very often swims in the surface of the water and now and then leaps into the air. Goode') says about the matter: „A sword-fish when swim- ming near the surface of the water usually allows its dorsal fin and the upper lobe of its caudal fin to be visible, projecting out of the water several inches. Sword- fishes are sometimes seen to leap entirely out of the water." Of Mola it is a matter of knowledge that it is seen lying in the surface of the water in such a manner that one should think it was sleeping (see Steenstrup and Liitken). When a Xiphiaa is leaping out of the water it is very possible that some air can remain between the branchial-lamellae, and this air may thus be used for respiration. I should be interesting to see the results of physiological exper- iments made with living animals. Unfortunately it will be rather difficult! List of Literature. I 1; Al essandr i n i. De Piscium Apparatu Respirationis. Novi Commentarii Academiae Scientiarum Instituti Bononiensis. T. III. Bononiae 1839. 2) C u V i e r, Anatomie Comparée. T. VII. Paris 1840. 3) Cuvier et Valenciennes, Histoire naturelle des poissons. T. VIII. Paris 1831. 4) Goode, Brown, The Fisheries and Fishery Industries of the United States. Section I. Washington 1884. 5) Liitken, Ichthyographiske Bidrag IV. Vidensk. Medd. Nat. Foren. Køben- ; havn 1875. 6) — Bidrag til Kundskab om Formforandringer hos Fiske. Vidensk. i Selsk. Skr, 5. Række naturv. og matem. Afd. XII. 6. Køben- i havn 1880. f
297 7) Steenstrup og Liitken, Bidrag til Kundskab om Klump- eller Maane- fiskene Molidae). Vidensk. Selsk. Skr. 6. Række, naturv. og matem. Afd. IX. 1. København 1898. 8) Tro i s, Osservazioni sull'intima struttura delle branchie del Xiphias gla- dius. Atti del reale Istituto Veneto di scienze, lettere ed årti. Tomo 1. Ser. VI. Venezia 1882-83. 9) Jordan & Evermann, The Fishes of North and Middle America. 1896 — 1898 Explanation of Piates. PI. XVIII. Xiphias glaciius. Fig. 1. Ossifications from the outer surface of hemibranch. Fig. 2. Ossifications from the inner surface of hemibranch. PI. XIX. Acanthocybium solnndri. Fig. 1. Ossifications from the outer surface of hemibranch. Fig. 2. Ossifications from the inner surface of hemibranch. Enlargement ca. 50 x. NB. The photos are placed transversally on the piates! 26—3—1919.