Nr. 1] ANATOMIC AL STUDIES ON ANELASMA AND SCALPELLUM 5 



Anelasma squalicola (Loven) Darwin. 



The coarser anatomy of Anelasma has been exeHently demon- 

 strated by Darwin (1851 p. 170), and I shall here restrict myself 

 to som topognaphic remarks which are of general interest in connec- 

 tion with the histological detail s. 



The parasites are generally found at the base of the dorsal or 

 anal fins of Etmopterus spinax. The parasite is very seldom 

 single; in most cases we find two specimens at the base of one 

 fin, but in some cases I have more specimens, in one case even five 

 in one duster. In a letter to Darwin, Jap. Steenstrup mentions 

 that there are always two individuals sitting together; this remark, 

 in connection with the hermaphroditic nature of the animals, 

 caused Gruvel (1905) to suppose that a cross fertilisation would 

 probably be found on closer investigation. I have not succeeded in 

 observing the act of fertilisation, and shall not discuss Gruvel's 

 supiposition bare; it has only to be remembered in this connection 

 that the ovaries and the testes in the individuals investigated ripen 

 at the same time in one animal. 



Embedded in the body of the shark we find the well developed 

 peduncle which is provided with rootlike filaments or offshoots. 

 Loven (1845), and as far as may be judged, also Darwin, merely 

 considered these filaments as organs of adhesion, serving to keep 

 the animal fixed in the shark's body. Kossmann (1874) on the 

 other hand, maintahis that the filaments are also nutritive organs, 

 and provide the parasite with most of its food at the oost of its host. 

 Also Geoffroy Smith (1906) seems to share this supposition 

 after a comparison of the filaments with similar organs of the 

 Rhizoc ep h al a. 



Textfig. I. Transverse sections of a small Anelasma squalicola, the free 

 part of which projects 1.5 mm above the sharks skin. a section through 

 the «stalk», b section through the thorax in the lower part of the pro- 

 boscis. [X 15]. D = Dorsal side; V= ventral side; m. = mantle; mc. = 

 mantle cavity; i. = digestive intestine; i. g. = digestive gland. 



