IN the many kind and favourable reviews of my book, “The Naturalist in Nicaragua,” exception has been generally taken to my speculations on the extent and effects of the ice of the glacial period. The subject is a large one, and too little of my time can be given to scientific inquiry to allow me to hope that I can deal with it in detail for some years to come; but as it appears that I have not expressed my views with sufficient clearness and have I been misunderstood by some of my critics, I shall be glad of an I opportunity to state them with distinctness and brevity.