xxiv] SIR CHARLES LYELL 425 



He then goes on to give illustrations of this, and urges 

 that there are no recent deposits in or near the tropics 

 containing fossil remains proving any change of fauna and 

 flora such as Darwin had advocated. He then continues — 



" I know of no evidence of this kind, and I don't think 

 that Darwin has given any time or thought to Croll's eccen- 

 tricity theory, or to my chapters upon it, and I wish much 

 that he could see your review ' before he came out with 

 this new edition (the fifth) of ' The Origin ; ' for I am 

 afraid that he will make too much of the supposed corro- 

 boration afforded by the imaginary warmth of the southern 

 hemisphere, and of the equally hypothetical expulsion of 

 tropical forms from the equatorial zone north of the line." 



In the sixth edition of "The Origin," published three 

 years later, Darwin still held to his views of the extreme 

 severity of the glacial epoch influencing even the equatorial 

 zone, and explaining the transmission of so many northern 

 types of plants and insects to the southern hemisphere, as 

 shown by the following passage : — " From the foregoing facts, 

 namely, the presence of temperate forms on the highlands 

 across the whole of equatorial Africa, and along the penin- 

 sula of India, to Ceylon and the Malay Archipelago, and in 

 a less 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 continents were every- 

 where tenanted under the equator by a considerable number 

 of temperate forms. At this period the equatorial 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 " 

 (P- 338). 



In my " Island Life " I have discussed at some length all 

 these facts, and many others which Darwin did not take 

 into consideration, and have explained them on the theory 



'My Quarterly Review article on " Geological Climates and the Origin of 

 Species," a proof of which Sir Charles had seen. 



