The Origin of Spone-spicules

Abstract

IT is to be regretted that Dr. Bidder (NATURE, February 28), before publishing his criticisms of my theory of the symbiotic origin of sponge-spicules, did not await the publication of the detailed evidence upon which that theory is based. I am loth to enter into controversy with him, but as his letter contains much that is misleading, I feel that I can scarcely pass it over in silence. He speaks of the observation (presumably mine) “that the first rudiment of the spicule in Stelletta is a skeleton-crystal on the tetra-hedral system.” I made no such observation. On the contrary, I endeavoured to show by observations on the silica pearls that the first rudiment is a minute granule resembling a Micrococcus.