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Show 192 ME. A. D. MICHAEL ON AN [Mar. 5, to ascertain with certainty whether this tube ends blindly or is the duct of a fourth salivary gland; m y opinion is that the latter is correct and that the tube is a fine duct coming from a small roundish gland lying close to the reniform gland. It is for this reason that I say above "at least three pairs of salivary glands," but as I have not been able to trace tbe communication with certainty I have thought it best not to draw this gland. The common duct runs to the upper surface of the chitinous bridge or lamella which is joined at its edges to the inner sides of the maxillary lip and forms a chitinous endo-skeleton in the rostrum upon which the mandibles rest. The c o m m o m duct penetrates this chitinous bridge, and runs forward for a short distance practically within its substance; the duct terminates by a bell-shaped mouth (db.) on the underside of the chitinous bridge. In addition to the paired glands above described, there is an azygous sausage-shaped gland (fig. 23, asg.) practically in the median line of the hind part of the rostrum. It is about 4 1 mm. long, with a diameter of about -02 mm., is a fleshy organ with an extremely small lumen, and lies between the paired _ fan-shaped groups of muscles which run from the sigmoid piece to the mandibles (see page 203). The duct from this gland is short and fine, and runs straight forward towards the buccal chamber. 1 have said above that I doubt whether there is sufficient evidence to justify us in asserting positively that the function of all these various glands is salivary only. The Male Genital Organs (Plate VIII. figs. 17, 18; Plate IX. figs. 23, 28). The male reproductive system differs in a remarkable degree from anything which has, to m y knowledge, been hitherto described among the Hydrachnidae, or, indeed, in any of the allied families. Schaub, for instance, in his species found a group of five pyriform testes on each side discharging by a common duct, which duct joined with its fellow from the opposite side to form a short unpaired duct leading into a long, much convoluted, duct, which he calls the vas deferens: this terminated in a short penis surrounded by muscles. Croneberg's Eylais shows a complicated network of testes entirely unlike anything found in the present species. Probably the nearest described organs are those of the species of Trombidium figured by Croneberg in his later work, ' Ueber den Bau von Trombidium '; but even these present most material differences from the form I a m about to describe. In Thyas petrophilus there is, on each side of the body, what appears to be a large testicular mass (figs. 17, 28, 23, T.), which immediately underlies the lateral portion of the ventricular ring. This testicular mass has an average length in fully-formed specimens of about -3 mm., by a thickness in a dorso-ventral direction of about -17 m m . in its thickest part. This mass is comparatively flat on its under (ventral) surface, and comparatively, although not quite, straight on its iuner side; but it is formed into two |