THE CASPIAN SEA 565 



According to his evaluation of the Caspian Sea fauna, Poriferae, Coelen- 

 terata, Turbellaria, annelides, higher crustaceans, hydrachnid molluscs and 

 fish comprise 308 species and 138 genera. Of these the endemic forms of 

 the Black, Azov, Caspian and Aral Seas comprise 263 species (89 per cent) 

 and 72 genera (52-2 per cent), among them 32 genera (23-2 per cent) and 174 

 species (58-9 per cent) of Caspian forms endemic in the strict sense. On the 

 other hand, among the 170 species of parasites 21 species are endemic forms 

 of the Caspian Sea. No endemic genera have been recorded among the 

 parasites. Among the separate groups of the autochthonous Caspian fauna, 

 Poriferae and Coelenterata are the first to attract attention. Four species of 

 Poriferae inhabit the Caspian Sea — two species of the genus Metschni- 

 kovia (M. intermedia and M. tuber culata) together with Protoschmidtia flava 

 and Amorphina caspia. 



All the four species belong to the Renieridae family of the Cornacuspongia 

 order. The four species of Poriferae are Caspian endemics, while the species 

 of the genus Metschnikovia are related to the Baikal Baicalospongia and 

 Ochrid Ochridospongia. 



One of the three autochthonous Caspian Coelenterata, Polypodium hydri- 

 forme, occupying an ambiguous place among the orders of the sub-class 

 Hydroidea, is a parasite on the ova of Acipenseridae inhabiting the basins 

 of the Caspian, Black and Aral Seas. The Medusa Caspionema (Moerisia) 

 pallasi, a strictly endemic form of the Caspian Sea, does not possess the hy- 

 droid stage ; it belongs to the Clavidae family (Leptolida order). The hydroid 

 Cordylophora caspia belongs to the same order ; in contrast to the Caspionema 

 it lacks the medusa stage. Cordylophora with some other forms probably 

 penetrated into the Caspian Sea when this was joined to the Baltic Sea by 

 canals in the last century ; it was widely propagated in the Caspian and has 

 migrated from it, by means of shipping, into different parts of the world ; 

 it has now become a cosmopolitan form (L. A. Zenkevitch, 1940). Cordy- 

 lophora is also known in the Kurun Lake (lower Egypt). 



M. Tikhy has recorded as early as 1916 the existence of a plankton hydroid 

 in the Caspian Sea ; he did not give a detailed description of it and no one 

 else has recorded it since. The three closely related forms of polychaetes 

 inhabiting the Caspian Sea — Parhypania brevispinis, Hypania invalida and 

 Hypaniola kowalewskii — of the Ampharetidae family, are typical Caspian 

 autochthonous forms. The first is found only in the Caspian Sea, and the two 

 others are known in the inlets and rivers of the basins of the Black and Azov 

 Seas. 



Manayunkia caspica (Sabellidae family), a Caspian endemic form, is 

 closely related to the Manayunkia of North America, Europe and Asia and 

 to those of Lake Baikal. Manayunkia possibly penetrated into the Caspian 

 Sea with the Arctic community forms in the post-glacial age; however it 

 does not have a cold-water aspect as other relict immigrants have, and its 

 occurrence (M. Bacesko, 1948) in the Danube is an indication of its earlier 

 (pre-Khvalyn) genesis and of its penetration into the Pontic basin from the 

 northeast by fresh-water routes. 



Among the Caspian autochthonous forms one of the most prominent places 



