| OCR Text |
Show 676 MR. F. E. BEDDARD ON NEW [Dec. 20, the other New Zealand Acanthodrilidae which I have so far had the opportunity of studying-so different that it was unnecessary to dissect the species in order to ascertain its distinctness. All the New Zealand Acanthodrilidae, with the exception of the present species, are either devoid of pigment in the skin, or, if pigment is present, the worms are of a brownish colour. Acanthodrilus smithi is (after preservation in alcohol) of a violet colour, the clitellum being whitish yellow; the ventral surface of the body is the same colour as the clitellum. The worms are slender, measuring up to 75 m m . in length with a diameter of 3 m m . at the widest part of the body. An individual of this size consisted of 114 segments. The prostomium completely divides the buccal segment, as it does in the New Zealand species Acanthodrilus novee-zelandice &c. The setae are paired and the pairs are equidistant, the body being thus divided into four equal areas. There is no difference in size between the setae of different segments. The clitellum occupies segments xiii.-xix.; it is saddle-shaped, and is not developed ventrally beyond the outermost of the two ventral setae. I could find no dorsal pores. The nephridiopores are very evident; they alternate in position from segment to segment, as is the case also with other species of Acanthodrilus from New Zealand. They sometimes lie in front of the dorsal, sometimes in front of the ventral setae. When they open in front of the ventral setae they appear to be particularly related to the outer of the two setae; when, on the other hand, they open in front of the dorsal setae, the orifice is in front of the innermost of the two setae which constitute the pair. The spermatothecal pores lie on the border-line between segments vii./viii. and viii./ix. They lie in front of and to the outside of the ventral pair of setae. The atrial pores (see fig. 1, p. 669) are upon segments xvii. and xix. ; their position corresponds exactly with that of the ventral pair of setae, which are absent from these segments. The ventral setae are, on the other hand, present upon the xviith segment; and the sperm-duct pores lie a little to the outside of and in front of these setae ; their position therefore corresponds more accurately to that of the spermatothecal pores than do those of the atria. The internal structure does not present any special points of interest, being on the whole very similar to that of the other New Zealand Acanthodrili. The nephridia are alternate in position, as in A. dissimilis; this peculiarity is confined, as regards the genus Acanthodrilus, to the New Zealand species. The dorsal blood-vessel is single ; there are four pairs of dilated hearts, the last of which is in segment xiii. The alimentary canal is furnished with a rudimentary gizzard, which needs a microscopical examination for its demonstration ; such as it is, it lies in segment v. There are no conspicuous calciferous glands, |
