8 
INTEODrCTION. 
already shown the havoc made amongst them by the oil-makers. This is the cause of 
their being nearly extinct on James and Indefatigable Islands, where they used to be so 
numerous. Admiral Fitzroy found a party on James Island making oil in 1835. 
" In Abingdon Island, where they are not numerous, I believe they are doomed to 
destruction directly the orchilla-pickers are placed on the island ; for a party of sixty or 
eighty men will soon hunt over this small island and discover every individual on it." 
This first effort of resuming and supplementing Fitzroy's and Darwin's investigations 
may, it is to be hoped, encourage others to complete what Commander Cookson had to 
leave unaccomplished. Hood, James, and South Albemarle are deserving of particular 
and early attention ; and, if no living and adult specimens can be obtained, any remains, 
especially fragments of carapaces and skulls, from those islands, as well as from Chatham, 
Indefatigable, and Charles Island (where the Tortoises are said to be quite extinct) will 
prove of value. It may also be remembered that all the Abingdon Tortoises found were 
males, and that, beside the skull and cervical vertebrte, we do not know the remaining 
bones, the entire animal which had been preserved in spirits having been lost during 
the homeward journey. 
H.M.S. ' Challexgee ' likewise paid a visit to the archipelago immediately after the 
' Peterel,' but without obtaining additional information. The Tortoises brought home 
in this vessel were obtained by, and transshipped from, the ' Peterel.' 
The instances of occurrence of the same form of terrestrial animal at widely distant 
points of the globe are more numerous than we find recorded in treatises on geo- 
graphical distribution of animals. They form the most interesting element in the 
investigation of this subject, inasmuch as they have a direct bearing upon, and will 
greatly assist in the solution of, the problems of the origin of species and the history of 
the distribution of animals. Of all those instances no one appears to me more remark- 
able than the reappearance of the " Indian " Gigantic Land-Tortoises in the Galapagos — 
not in typical singularity, but with nearly all the principal secondary modifications 
reproduced. How can this be explained with the aid of the doctrine of either a 
common or mxanifold origin of animal forms ? 
On the hypothesis that there is no immediate genetic relationship between the 
Tortoises of the Galapagos and Mascarenes, we may assume, without overstepping too 
far the limits of probability, that some terrestrial Tortoises were carried by stream and 
current, or some other agency, from the American continent to the Galapagos, and 
that others from Madagascar or Africa found in a similar manner a new home in the 
Mascarenes. These Tortoises may originally have differed from each other, like the T. 
tdbidata, radiata, and sulcata of our days, possibly not exceeding those species in size ; 
but, being placed under similar external physical conditions evidently most favourable 
for their further development, they assumed in course of time the same gigantic pro- 
portions and other peculiarities, the modifications in their structure which we observe 
