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Show 1903.] ENTO-PARASITES OF THE " SKEAT EXPEDITION." 147 sion. The number of calcareous bodies is small, and other deeply staining structures, e.g. the nuclei and muscle-fibres,are but sparsely scattered through the tissues. There is a four-cornered nerve-mass well lying about the level of the juncture of the anterior one-third with the posterior two-thirds of the bothria, and this gives off four strands which pass peripherally and probably supply the bothria and introverts. I did not see any longitudinal nerves, though probably they exist. In his exhaustive monograph * " Recherches sur les Tetra-rhynques," Vaullegeard records his opinion that the numerous species of Tetrarhynchous Cestodes belong to but one genus, Tetrarhynchus. Raillet has pointed out that the generic name Rhyncobothrius Rudolphi, 1819, has precedence of Tetrarhynchus 1809, the latter name having been given to a larval form. In the present case, although it may be inconsistent with the laws of nomenclature, I have followed Vaullegeard, partly because everyone knows what Tetrarhynchus is, and partly because, in my opinion, needless confusion is introduced into the study of tapeworms by using a double nomenclature for larva? and adults. In civilized society it is not considered necessary for a human being to change his name when he leaves the home of his childhood and sets up in a new house, and there seems as little reason for a young Oestode to change its name when it changes its host. Vaullegeard arranges the various species into two sections, one of which, on the type of T. lingualis Cuv., has in its larval form no vesicle projecting over and protecting the head. To this section the cestocle in question belongs. The larvse which were collected by the Skeat Expedition were some of them wholly and some of them partly enclosed in cysts, but none of them showed any trace of the projecting vesicle. Tetrarhynchus holothurice, n. sp. (Plate XVI. figs. 5, 6, & 7.) The larval form (but not the encysted form) is 6 m m . long by 1 m m . broad. Tapering posteriorly where there is a depression receiving the excretory pore. The two large bothria are subdivided by a ridge. The four introverts are provided with a cap of hooks pointing forward at the tip and a circular band of hooks pointing backward, between these two toothed regions is a considerable portion devoid of hooks. Habitat. A common Holothurian, probably a Molpadia, taken off the mouth of the Patani River. TETRARHYNCHUS sp. (Plate XVI. figs. 8 & 11.) Some eight or nine small cysts about the size of very poor wheat-seeds were taken from the body of a sea-snake, Enhydrina vala-kadien Boie. Unfortunately the position of the cysts in the body is * Mem. Soc. Normandie, xix. 1897-1899, p. 185. 10* |