November 1, 1901.] 



SCIENCE. 



695 



and important communication between the In- 

 dian Ocean and the Mediterranean, as is shown 

 by several interesting cases in the distribution 

 of Crustaceans,* although it is impossible to say 

 whether what is now the Isthmus of Suez 

 played an important part in this question ; the 

 connection may have been somewhere else. 



3. The Cape of Good Hope as a zoogeographical 

 barrier. 



Professor Jordan does not believe that the 

 Cape of Good Hope offers an absolute obstacle 

 to a migration of tropical Indo-Pacific species 

 into the Atlantic, I do not hold the same 

 opinion. Indeed, we know that the tropical 

 fauna of the Indian Ocean extends southwest- 

 ward along the coast of Natal and the Cape 

 Colony, and some elements of it go even as far 

 as Cape Town. But if we follow the shore line 

 from here northward, along the western coast 

 of Africa, we meet a considerable change of the 

 clioaatic conditions, for from this point almost 

 to the equator cold water is found. While it is 

 thus true that the fauna of the Cape of Good 

 Hope, as President Jordan says, shows a gen- 

 eral relation to that of India and Australia, this 

 applies only to the southern and the southeast- 

 ern shores of the Cape Colony, while the west- 

 ern (Atlantic) side, together with the adjoining 

 coast of southwest Africa, about as far as the 

 mouth of the Congo, forms an impassable bar- 

 rier to this tropical fauna of the Indo-Pacific. 



4. The Isthmus of Panama. 



It is beyond doubt that the Atlantic and Pa- 

 cific Oceans were once connected with each 

 other within the tropics : this connection ex- 

 isted up to the middle of the Tertiary, and it 

 was closed during Miocene times. For this 

 general assumption we possess an overwhelm- 

 ing mass of evidence. The question remains : 

 Where was this connection of the two oceans 

 situated? Formerly it was the general trend 

 of opinion to assume a former depression of 

 the Isthmus of Panama, but since Dr. R. T. 

 Hill has shown that there are serious objections 

 to this on geological grounds, we have to modify 

 this theory. The present writer has tried f to 

 do so with respect to v. Ihering's Archiplata- 

 Archhelenis theory ; the connection of the At- 



*See Ortmann, 1. c, p. 1276. 



fin Science, No. 311, 14 December, 1900, p. 929. 



lantic and the Pacific in the Tertiary times was 

 identical with the ' sea separating Archama- 

 zonas and Archiplata, that is to say, aci'oss the 

 South American continent about where there is 

 now the Amazonas valley ' — the Cordilleras 

 not existing then. 



5. Explanation of the distribution of Oalaxias. 



The genus of freshwater fishes, Galaxias, is 

 represented only in South Australia, New 

 Zealand, South America and South Africa,* 

 and it has been taken as one of the instances 

 which demonstrate the former connection of 

 these parts by land, the Antarctic continent. 

 Professor Jordan hesitates to accept the latter, 

 and his chief arguments are : (1) That this sup- 

 posed continental extension should show per- 

 manent traces in greater similarity in the pres- 

 ent fauna both of rivers and of sea, and (2) 

 that geological investigation must show reasons 

 for believing in such radical changes in the 

 forms of continents. 



As to the first point — although this connec- 

 tion is quite remote in time — the cases of simi- 

 larity in the present marine, fresh-water and 

 land faunas are very numerous, and there is 

 hardly any larger group of animals where 

 such are lacking. This fact has been discussed 

 by a large number of writers, f and the wealth 

 of evidence brought to light compels us to rec- 

 ognize this Antarctica theory as well estab- 

 lished. As to the second point, the geological 

 proof for existence of ' Antarctica,' I refer only 

 to Professor J. W. Gregory, J who has shown 

 that the tectonic configuration of Australia, 

 New Zealand, South America and Antarctica 

 — as far as we have any knowledge of the 

 last — only tends to support the assumption of 

 a former connection of these parts. That there 

 is, generally speaking, ample reason for believ- 

 ing in ' radical ' changes in the form of conti- 

 nents during the earth's history, has been dem- 

 onstrated by geologists long ago, although it 

 has become almost a fashion among biologists 

 to disregard this line of evidence. 



Princeton University. A. E. Ortmann. 



* South Africa is not mentioned by Professor Jordan. 



t The most important are mentioned by the present 

 ■writer in the American Naturalist, 35, No. 410, Feb., 

 1901. 



t Nature, Vol. 63, 25 April, 1901, p. 609. 



