What India has been in the past 300 years to our Army as a nursery in which our soldiershave obtained experience in their profession and earned their promotion, often to the highestrank, such in a lesser degree has it been to many of our geologists, who have, in the past much shorter period of 50 or 60 years, entered the service in this vast field of scientific enterprise, and, aided by a very few amateur geologists in the Army and of civilians attached to other branches of Government employ, have covered many thousand square miles of our Indian Empire with records of their untiring energy in the geological field.

The object of this communication is to try to give a theory of what takes place when one species ischanged into another. When the species A is converted into the species B there must be an intermediatetransitional stage in which the collection of individuals is neither the species A nor the species B. I have already defined a species as a centre round which individuals are thickly clustered, and the spaces between these centres may be either devoid of individuals or contain here and there an abnormal form (Davidson's “ Suppt. Jurassic Brachiopoda,”Pal. Soc, 1876, p. 122).

I was much interested in the account of the ‘erosion’ of rocks in Corsica given by Mr. Tuckett and Professor Bonney respectively in the January and August numbers of the GeologicalMagazine for 1904, more especially as I have been long acquainted with similar phenomena in Madagascar, and have, equally with the authors mentioned, been long puzzled to find an explanation of their origin at all satisfactory.

Since it has been proved that large areas of basaltic and other igneous rocks withinor near the Tropics in India, on the Seychelles, and in Australia yield surface deposits (so-called Laterites) identical with Bauxite, it is of great importance to ascertain exactly what products of decomposition or weathering originate from corresponding rocks in a temperate climate.