MAlilNE FOKMS IN FliESH WATEE. 147 



common also in the magnificent Laguna de Bay near Manila. 

 Sea-fistes, which normally live also in fresh water, or which 

 thrive well when introduced into it, are by no means rare ; 

 thus Peters found Rays deep in the heart of East Africa ; the 

 Lake of Acqua, near Padua, which is of pure fresh water, has 

 become famous by the success of an attempt made there to breed 

 sea-fish — Mugil (the grey mullet) and Labrax (the basse) — in 

 great numbers for the market. Among the Invertebrata such 

 cases are yet more common. Palczmo'ri, a genus of Crustaceans 

 which inhabit fresh water almost exclusively, belongs to a 

 family which generally includes none but marine animals ; 

 various species of this genus live in rushmg mountain streams 

 in the Philippines, and are found at an elevation of 4,000 feet or 

 more above the sea. In the branchial cavity of this Crustacean 



6 



Fig. 38. — Bopynis aKendms. a, the lower ; 6, the upper side. It lives in the gill-cavity 

 of Paltsmon or)iat7ts (Oliv.), and is found with it ascending fresh-water streams at a 

 height of 4,000 feet above the sea. All the other knovvn species are marine. 



lives a species, as yet undescribed, of the genus Bopyrus (fig. 38), 

 which I have named Bopyrus ascendens. It is the only fresh- 

 water form hitherto known, while the other very numerous 

 species live exclusively in the branchial cavities of sea crabs. 

 Aucapitaine states that a true Cyprcea — the species known as 

 the money-cowry — is caught in the interior of Africa, near 

 Timbuctoo, in quantities' by the natives ; various molluscs of 

 the family of ship-borers — Nausitara Duidopi (Wright) and 

 Teredo senegalensis (Blain.)^-and of the Pholadidas — Martesia 

 rivicola — live in the rivers of India and Java, while all the 

 other species of these families are true marine creatures. I ate 

 oysters (fig. 39) at Basilan in the south of Mindanao, which, 

 although they had a salt flavour and were indeed bathed 

 by brackish water at high tide, yet at ebb tide were surrounded 



