Miscellaneous . 181 



The latest changes are accomplished after the escape of the embryo 

 of Gehia littoralis from the e^g. — Zool. Anzeiger, xvii. Jahrg., 

 no. 452, July 16, 1894, pp. 253-256. 



On Gill-like Organs in certain Species of Sipun cuius. 

 By Dr. W. Fischee, of Bergedorf. 



That the tentacles in Sipunculidce possess the faculty of respi- 

 ration was formerly a matter of almost universal belief. Lately, 

 however, at least in respect of certain genera, many doubts have 

 been expressed as to this. It had already been pointed out by 

 Brandt *, that in the case of Sipunculus niidus, L., the extraordinary 

 thickness of the layers of connective tissue in the tentacles would 

 militate against the view that respiration could be effected by 

 means of these organs. The same conclusion is also deduced by 

 Ward t, who had the opportunity of observing the living Sipimculus 

 nudus in an aquarium at widely different times and in very various 

 situations. This author states that he has seldom seen the tentacles 

 extruded and never for a longer period than from one to two 

 seconds : in the retracted condition he does not believe that they 

 can be of any importance whatever for the purpose of respiration. 

 Moreover, he adds that since no connection can be shown to exist 

 between the blood-vascular system and the coelome, the peripha- 

 ryngeal vascular ring and the two short contractile vessels would 

 present far too small a surface to the body-cavity to be able to 

 convey sufficient oxygen from the blood-vascular system to the 

 latter. 



If it was thus impossible in the case of Sipunculus nudus to 

 concede to the tentacles the possession of a respiratory faculty, it 

 was natural to suppose that the skin might possibly be able to 

 discharge this function. In his paper on Sipmnculus nudus, 

 Andrese J had already described dermal canals, which traverse the 

 entire body and lie in the region of the cutis close beneath the 

 cuticle and hypodermis ; the author terms these structures integu- 

 mentary canals (Integumentalcanale). He found them generally 

 packed with ova and blood-corpuscles, and he maintains that the 

 dermal layer, which separates them from the exterior, is sufficiently 

 thin to enable an exchange of gases to take place between the 

 coelomic fluid and the sea- water. Ward, too, agrees with this 



* Alex. Brandt, " Anat.-histologische Untersuehungen iiber Sipunculus 

 nudus, L.," M^moires de I'Acad. imp. des Sciences de St. Petersbourg, 

 1870, torn. xvi. no. 8. 



t H. B. Ward, " On some points in the Anatomy and Histology of 

 Sipunculus nudus, L.," Bull. Mas. Oomp. Zool. xxi. (1891) pp. 143-182 

 (3 pis.). 



X Audrese, " Beitrage zur Anatomie und Histolosie des Sipunculus 

 nnda.^;' Zeitacbrift f. wiss. Zoologie, Bd. 36, pp. 201-208. 



