Report on a Collection of Cestoda, mainly from Egypt. Part II. Cyclophyllidea: Family Hymenolepididae

Abstract

In cestodes of this family, the number, size, and shape of the rostellar hooks is needed for the identification of the species. While number and size are often quoted (e.g. Fuhrmann, 1924 a) the shape is usually ignored owing to the impossibility of reproducing innumerable figures: this greatly lessens the usefulness of such lists as the one above mentioned, especially to workers not in touch with a well-stocked library. For this reason the formula illustrated in Text-fig. 1 is suggested. The base, AB, of the hook is considered as unity and other measurements are expressed in decimals of it. EH is a tangent drawn parallel to AB and touching the hook at its highest point H; GB, FC and KL are perpendiculars drawn from AB to the two extremities G, F of the hook and to the inside, K, of the curve FG. With the points A, G, H and K fixed the approximate shape of the hook is determined: the various formulae may then be compared or the hook itself be reconstructed. Text-fig. 2 gives examples of the various types of hooks and their respective formulae, Text-fig. 3 of their reconstruction from the formulae. This arrangement appears preferable to that of Stevenson (1904) as being simpler and also facilitating reconstruction.