248 Dr. Max Weber on the 



water animal. The freshwater form described by von Martens 

 and myself perhaps also already differs somewhat from the 

 marine form. At any rate, it follows that we are acquainted 

 with this species from the sea (Bay of Bengal), from a river 

 (Kapuas River), and from an elevated freshwater lake (Lake 

 of Singkarah). Passive immigration — of coursewith a certain 

 amount of assistance on the part of the animal itself — may 

 therefore probably be assumed in this case also. 



The occurrence of Tachwa lacustris, sp. n., upon Cyprinoids, 

 likewise in the Lake of Singkarah, is to be explained in a 

 similar manner. This new species differs but little from 

 Tachcea crassi2)es, Schiodte and Meinert, which von Martens 

 discovered upon the coral-reef of Singapore, consequently 

 under conditions as marine as possible. 



According to the mode of explanation which has prevailed 

 hitherto the Lake of Singkarah consequently contained two most 

 excellent examples of genuine relic-animals ; later on we shall 

 be able toindicateyet other marine forms from the same locality. 

 An immigration on the part of these animals into this lake is, 

 however, the much more natural explanation of their presence, 

 and is at the same time in accordance with the geological 

 facts, which furnish no proofs that the region of the lake, 

 either during or subsequent to the formation of its basin, was 

 inundated by the sea, or that tlie lake was at any time filled 

 with sea-water. 



Moreover other species of Cyraothoince are known, which 

 have become adapted to freshwater life, but occur especially 

 in the lower courses and at the mouths of rivers — indications 

 that it is immigration with which we are dealing in this 

 instance. 



Besides my three species mention must be made of Ichthyo- 

 senus montanus, Schiodte and Meinert, already alluded to, 

 from rivers of the Himalaya ; also of two species that appa- 

 rently are allied to this — Lironeca laticauda^ Miers, from 

 Manchuria, and Lironeca daurica, Miers, from the Biver 

 Onon in South-east Siberia — and, further, of Cymothoa amu- 

 rensis, Gerstf., in Siberian rivers, and Asotana formosa^ Sch. 

 & Mein., from the Biver Icja in Peru. 



The following species were found at the mouths of rivers, 

 or, at any rate, in the adjoining lower portion of the stream : — 

 Neroclia jiuviatilis, Sch. & Mein., in the Bio Plata near 

 Monte Video ; Lailircena insidiosa, Sch. & Mein., in the 

 mouth of the Biver Santos, in Brazil, upon CentengrauUs 

 edentu/us ; Telotha lunaris, Sch. & Mein., in the Bio das 

 Velhas, Brazil, upon Sternarchus hrasiliensisy Bht. ; Telotha 

 Jlenselii, v. Mart., in a river near Porto Alegre, Brazil, upon 



