Page:Transactions NZ Institute Volume 33.djvu/128

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entire specimens stained and cleared. From the point of view of the comparative anatomist the results obtained are hardly sufficient to compensate for the large expenditure of time and trouble, as in most respects the anatomy seems to agree very closely with that previously known for other species of the genus. The structure and arrangement of the nephridia, however, appear to be very peculiar, though we have not succeeded in working them out in detail, and the presence of only two annuli in the typical somite appears to distinguish our species not only from others of the same genus, but from all other Rhynchobdelliadae.[1]

External Characters.

In contracted specimens the body is ovoid; emarginate and somewhat broader behind; strongly convex above and concave beneath, so that there is a large hollow space below the body which serves as a brood-pouch; with no distinct head. The length of a spirit-preserved specimen was 6 mm., and the width 4 mm., with posterior sucker l.5mm. in diameter. Another specimen, when extended in life, measured as much as 18 mm. in length. The animal in life is of a very pale dull orange or flesh-colour, semitransparent, with no papillae nor colour-markings except microscopic pigment-cells. In spirit the colour is almost white, opaque.

The posterior sucker (disc) is flat, and usually nearly circular in outline; in contracted specimens scarcely visible from above. The much smaller anterior sucker appears to be made up of from five to eight annuli[2] (it is impossible to determine the exact number), and its anterior margin, forming the extreme anterior end of the body, bears a slight median notch.

On the dorsal surface of the body about fifty-five annuli may commonly be counted, but the annulation is not sufficiently distinct and regular to make an exact count practicable. In the middle region of the body it is evident, from the arrangement of the nephridial apertures and various internal organs, that each somite is composed of two annuli.

The eyes are four in number, placed two on each side of the middle line, those of the same side very close together, sometimes touching one another, so as to appear as one in contracted specimens, but separated from those of the opposite side by a fairly wide interval. Their position is about on a level with the hinder margin of the anterior sucker. Those of one side may be distinctly in advance of those of the other side, and the position as regards the annuli of the head seems

  1. ↑ See Postscript, however.
  2. ↑ In counting the annuli we assume throughout this paper that the head (anterior sucker) is made up of eight.
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