A Monograph

Excerpt-The Lepadidæ, or pedunculated Cirripedes, have been neglected under a systematic point of view, to a degree which I cannot quite understand: no doubt they are subject to considerable variation, and as long as the internal surfaces of the valves and all the organs of the animal's body, are passed over as unimportant, there will occasionally be some difficulty in the identification of the several forms, and still more in settling the limits of the variability of the species. But I suspect the pedunculated Cirripedes have, in fact, been neglected owing to their close affinity, and the consequent necessity of their being included in the same Work with the Sessile Cirripedes; for these latter will ever present, I am fully convinced, insuperable difficulties in their identification by external characters alone.