[A histo-anatomical study on the spleens of a frilled shark, Chlamydoselachus anguineus].

The spleens of a frilled shark, Chlamydoselachus anguineus was histo-anatomically studied. The results were as follows. 1. Two independent spleens, one in the dorsal mesogastrium and the other in the ventral mesenterium (Ligamentum hepatoduodenale), are noted. Splenic branches are provided either from a. lienogastrica for the former or from Truncus coelomesentericus for the latter. The venous system holds a non-collateral position to the arterial system and drains the intrasplenic blood by complicate routes. The vascular architecture of the intestinal tract of Chlamydoselachus is same as that of the sixgill shark, Hexanchus. 2. Histologically, both spleens consist of the white pulp (arteries and periarterial lymphatic sheath) and the red pulp. No active hemopoiesis is noted. Ellipsoids are present around arterial terminals. Arterial terminals communicate directly to venous vessels of the red pulp. Both incompletely-formed collateral veins of intrasplenic arteries and capsular drainage veins are noted. These features are essentially same as those of other elasmobranch spleens.