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Show 104 MR. F. F. LAIDLAW ON POLYCLADS [May 26, rows extending forward from over- the brain. They are mostly of small size, but immediately over- the brain there are on either side some half-a-dozen eyes of a much greater size than the rest. Text-fig. 4. i \ IJ Disparoplana dubia, sp. nov. X 4 circ. Unfortunately the solitary specimen is not in a very satisfactory state of preservation. The epidermis has almost completely disappeared, and the body is much distended with ripe eggs, so that the characters of the gut are difficult to determine. The pharynx is folded and of the usual Acotylean type. The brain is protected by a sheath of unusual toughness. Genital Organs. Male apparatus.-The terminal parts consist of a cylindrical penis lined with short chitinous spines, of a small prostate gland, and of a muscular vesicula seminalis (PI. IX. fig. 2). The resemblance to the corresponding organs in Planocera or Paraplanocera is very close. The male aperture is very small and opens into a narrow tube which runs forwards and a little upwards. The cells lining it give off a granular secretion. After a course of about 1 m m . this passage widens out to become the lumen of the penis. This organ is proportionately longer than in Planocera and a little coiled ; but shorter than in Paraplanocera. Its walls are not very stout, and the muscle-fibres which form them are continuous with those that surround the prostate. The spines lining the lumen bear a close resemblance to those of Planocera; but the diameter of the penis is relatively less. The prostate is small, but similar to that of Planocera. Its duct is joined by the ductus ejaculatorius running to the penis from the relatively large vesicula seminalis which lies in front of the prostate and receives |