172 THE ORIGIN OF SPECIES 



Besides these identical and closely allied forms, many 

 species inhabiting the same widely sundered areas belong 

 to genera not now found in the intermediate tropical 

 lowlands. 



These brief remarks apply to plants alone; but some 

 few analogous facts could be given in regard to terres- 

 trial animals. In marine productions, similar cases like- 

 wise occur; as an example, I may quote a statement by 

 the highest authority, Prof. Dana, that "it is certainly 

 a wonderful fact that New Zealand should have a closer 

 resemblance in its Crustacea to Great Britain, its antipode, 

 than to any other part of the world." Sir J. Eichardson, 

 also, speaks of the reappearance on the shores of New 

 Zealand, Tasmania, etc., of northern forms of fish. 

 Dr. Hooker informs me that twenty -five species of Algae 

 are common to New Zealand and to Europe, but have 

 not been found in the intermediate tropical seas. 



From the foregoing facts, namely the presence of 

 temperate forms on the highlands across the whole 

 of equatorial Africa, and along the peninsula of India, 

 to Ceylon and the Malay Archipelago, and in a less 

 well-marked manner across the wide expanse of tropical 

 South America, it appears almost certain that at some 

 former period, no doubt during the most severe part of a 

 glacial period, the lowlands of these great continents were 

 everywhere tenanted under the equator by a considerable 

 number of temperate forms. At this period the equa- 

 torial climate at the level of the sea was probably about 

 the same with that now experienced at the height of 

 from five to six thousand feet under the same latitude, 

 or perhaps even rather cooler. During this, the coldest 

 period, the lowlands under the equator must have been 



