164 ALTERKATE GLACIAL PERIODS [Chap. XIL 



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

 tainly a wonderful fact that ISTew Zealand should have 

 a closer resemblance in its Crustacea to Great Britain, 

 its antipode, than to any other part of the world." Sir 

 J. Richardson, 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 prob- 

 ably 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 

 temperate 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 Fer- 

 nando Po, in the Gulf of Guinea, Mr. Mann found tem- 

 perate European forms beginning to appear at the height 



