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Show 1896.] FROM THE SANDWICH ISLANDS. 197 throughout. On the very first seta-beariug segment of the body the setae have precisely the same ridged free extremities that the setae upon the clitellum show. At first the seta) of each pair are fairly close together. Later they get farther apart and become irregular in arrangement, as in Pontoscolex corethrurus. On the clitellum the ventral pairs are quite regular, although each individual seta of the pair is farther away from its fellow than anteriorly. This continues for a short distance behind the clitellum. On the other hand, the lateral pairs of setae are irregular in the clitellar region. The ventral of the two setae, however, which is on a line with the nephridiopore, is fixed in position : it is the other which varies. The clitellum occupies segments xiv.-xxi. with a portion of xiii. and xxii. The dorsal vessel is in certain respects peculiarl. Where it emerges from the last thick mesentery it is moderately thin; it gradually becomes thicker and at the same time monihform; the increased thickness is due to the fact that the dorsal vessel becomes double ; its character is that of the dorsal vessel in Acanthodrilus novce-zelandice, i. e. the tube is single where it traverses the septa, but separates into two halves between the septa. In segments xiv. and xv. the dorsal vessel attains to its greatest bulk; after this its calibre becomes suddenly diminished. It retains, however, its double character. In segments xi., xii. are hearts which seem to have no connection with the dorsal vessel but only with the supra-intestinal. The gizzard is in segment v.; it is followed by four very thick septa. In the segments following the gizzard are 3 pairs of calci-ferous glands. Behind the first three strong septa are very small spermatothecae, simple elongate oval pouches without diverticula. Hab. Mauna Loa, Hawaii, and Waiahia, Oahu. Perichceta indica, Horst. Dr. Michaelsen has called attention2 to the fact that this species, which is very widely distributed, is frequently without a " prostate" gland. In five specimens which he received from Georgia and Florida there was no trace of the gland, only the muscular duct being present. In the 6th specimen the gland was present on one side. Dr. Michaelsen further makes the suggestion that the original home of the species may be Japan, where as a general rule3 the Perichcetce show the same character. Among the worms collected by Mr. Perkins were 8 examples of this species from Molokai, all fully mature ; I dissected seven of them, in none of which was there the least trace of the gland in question; the curved duct alone was present. 1 In one specimen of three which I examined, the dorsal vessel seemed to be single. 2 "Die Eegenwurm-Fauna von Florida u. Georgia," Zool. JB., Bd. viii. p. 177. 3 F. E. Beddard " O n some Perichsetidae from Japan," ibid. Bd. vi. p. 755. |
