My endeavours to establish a genetic relationship between the Annelida and the Phyllopod Crustacean Apus led me, very naturally, to the study of the Trilobites. Specimens were kindly lent me by Dr. Woodward, F.R.S., Prof. Judd, F.R.S., and by Prof. G. B. Howes, it being my privilege at the time to be working in the Huxley Research Laboratory, which is under his direction.

Picking at the fossil with a steel point taught me, what every worker soon finds out for himself, that the limbs which, under such a dorsal shield, would probably have been thin-walled structures, could not be differentiated from the matrix by any such method. Was there, then, no mechanical method of revealing the undersurface? At first I thought, among other things, of a stream of water, mixed with emery powder, forced through a rose; this idea led, very naturally, to the sand-blast. a visit to the London Sandblast “Works” (58A, Gray's Inn Road) gave some promise. The proprietor was kind enough to express interest in the idea, and showed me blocks of granite which had been treated with the sand-blast, and in which the harder elements stood outingood relief. a very short application of one of the sand-blasts belonging to the Works to the under-surface of a Trilobite from the soft Wenloek cleared away a large portion of the matrix, and revealed a small area of the under-surface of the carapace completely cleaned.inthis specimen there was no trace of any under membrane having been cut through, and the carapace was probably the last remnant of a cast skin.