THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[FOURTH SERIES!] 



No. 68. AUGUST 1873. 



X. — On the Invertebrate Animals of the Baltic. 

 By Prof. Karl Mobius.'* 



Faunistically the Baltic is sharply divided into an eastern 

 and a western basin. The western basin is separated from 

 the Kattegat by the Danish islands. I do not include the 

 Belts and the OEresund in the western basin when I speak of the 

 fauna of the latter. The eastern basin meets the western one 

 in the meridian of the west coast of the Isle of Riigen. 



Of the 241 invertebrate animals catalogued, 216 species 

 have been found in the western, and hitherto only 69 in the 

 eastern basin. 



Besides those mentioned, Acarina, Ostracoda, Infusoria, and 

 Rhizopoda exist in the Baltic ; but their enumeration must be 

 postponed until the species have been determined with more 

 certainty, for which purpose further investigations are neces- 

 sary. 



Among the Infusoria, however, I will refer to Peridinium 

 tripos, Mull.f, which appears in great abundance during the 

 summer and autumn in the bay of Kiel as a luminous animal, 

 and is of importance as food for Copepoda and the swarming 

 embryos of other Invertebrata. 



* Translated by W. S. Dallas, F.L.S., from the concluding remarks 

 appended by the author to the list of the Invertebrata of the Baltic, pre- 

 pared by him with the assistance of Profs. Kt KupfFer, E. Hackel, W. 

 Schmidt, and of Dr. Butschli, and published as part of the report on the 

 scientific results of the expedition of the steamship ' Pommerania ' in 1871 

 (pp. 138-141). 



T Ehrenberg, ' Infusionsthierchen,' p. 255, pi. 22. fig. 18. 

 Ann. & Mag. N. Hist. Ser. 4. Vol. xii. 6 



