Decapod anatomy Decapod anatomy The decapod crustacean, such as a crab, lobster, shrimp or prawn, is made up of 20 body segments grouped into two main body parts, the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various groups these may be reduced or missing. They are, from head to tail: The head also bears the (usually stalked) compound eyes. The distal portion of a mandible or maxilla which has a sensory function is known as a palp. Maxillipeds are appendages modified to function as mouthparts. Particularly in the less advanced decapods, these can be
On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection of two indefatigable naturalists, Mr. Charles Darwin and Mr. Alfred Wallace. The gentlemen having, independently and unknown to one another, conceived the same very ingenious theory to account for the appearance and perpetuation of varieties and of specific forms on our planet, and both fairly claim the merit of being original thinkers in this important line of inquiry; but neither of them having published his views, though Mr. Darwin has for many years past been repeatedly urged by us to do so, and both authors having now unreservedly placed their papers in our hands, we think it would best promote