DISPERSION AND DISTRIBUTION. ]xxxiii 



hawk or eagle have secured such a fish and carried it away to the mountains 

 in order to feed its young or consume it at its leisure, should the eggs fall 

 into water they might similarly hatch and the breed spread. Geese and 

 ducks (or even flying insects, as some beetles) might likewise spread fishes 

 or convey the ova partially frozen attached to their bills or feet, while it has 

 been suggested that they might likewise be conveyed among the wet feathers 

 of birds or the fur of otters.* Among such forms as the perch, wherein we 

 see stringy ova, such might be carried long distances attached to sticks or. 

 grass or even to the feet of herons, grebes, &c. McCleay (Proc. Linn. 

 Soc. N. S. W., iii, p. 15) notices how a marine fish, Therapon unicolor, had 

 been found in a dam near Warialda, to which place the ova was supposed to 

 have been conveyed by birds : Davy also suggests that glaciers may have 

 assisted in the dissemination of ova.f 



DISPERSION AND DISTRIBUTION OF FISHES. . 



That marine fishes may become temporary or permanent occupants of 

 fresh waters and so change their condition of life has been observed by fish 

 culturists for centuries. Anadromous forms as the salmon ascend into fresh 

 waters to breed, there its eggs are hatched and the young reside until suffi- 

 ciently mature to follow their parents' mode of life. Should the return of 

 marine species to the sea be prevented, this is not necessarily fatal, for the 

 form may take on a fresh-water life. In the tropics it is common to find true 

 marine fishes in pieces of fresh water not far removed from tidal influence, 

 due to their having entered these places while the monsoon rains were at their 

 height, the rivers and swamps full, when .they had become carried, perhaps 

 by a high spring-tide, over a bank, but as the waters fell they became 

 imprisoned in their new situation and unable to return to the sea. Similarly 

 sea-fishes rove into our fresh waters after food, conclusively proving that such 

 change does not necessarily occasion their death, while here they may remain 

 and continue their race as observed in the northern portion of the Baltic 

 (i, page 54). 



In India, marine fishes are frequently observed ascending rivers for 

 predaceous purposes as far as the tide extends or even further. Therapous 

 are not uncommon in the Hooghly near Calcutta, while I have taken a sea- 

 perch, the " cock-up," Lates calcarifer, as far inland as in the river at Pegu 



* Pontoppidan (Natural History of Norway, ii, p. 139) remarked that at the top of Varne-set 

 and many other high places in Haranger, fish are taken in ponds which have no communication with 

 other ponds or rivers. He suggests whether they have been there since the flood; or 'if birds of 

 prey have carried the spawn or young fry up there. 



f Dr/Stoliczka found fishes living in Tibet in fresh water 16,000 feet abpve the level of the sea, ' 



. 



