164 ALTERNATE GLACIAL PERIODS [Chap. XII. 



by the highest .authority, Prof. Dana, that "it is cer- 

 tainly 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/ 1 ' 

 Sir J. Bichardson, also, speaks of the reappearance on 

 the shores of New Zealand, Tasmania, &c, 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 con 

 siderable number of temperate forms. At this period 

 the equatorial climate at the level of the sea was pro- 

 bably 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 clothed with a mingled tropical and temper- 

 ate vegetation, like that described by Hooker as growing 

 luxuriantly at the height of from four to five thousand 

 feet on the lower slopes of the Himalaya, but with 

 perhaps a still greater preponderance of temperate 

 forms. So again in the mountainous island of Fernando 

 Po, in the Gulf of Guinea, Mr. Mann found temperate 

 European forms beginning to appear at the height of 



