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Show 262 ON EARTHWORMS FROM NEW ZEALAND. [Nov. 15r The occurrence of a prostate in Megascolides australis, similar to that of a typical Acanthodrilid, seems to indicate that the confinement to a single segment is related to the cylindrical form ; and it is admitted by Michaelsen that these " Cryptodriline worms, belonging to the subfamily Megascolecinse, are derived from the subfamily Acanthodrilinse. And, on the other hand, the peculiar form of the gland in Notiodrilus aucklandicus illustrates the relation between a looser structure and the extension of the gland through several segments. But, although this transition of form between the " tongue-shaped " and " cylindrical " tubular prostates seems to occur, yet the flattened form appears a still later development; it occurs, for example, in the more modified genera, such as Pheretima. Miss Sweet has pointed out that in the " tubular " prostate there is a lumen running the whole length of the gland; whereas in the lobate form of this organ there is, typically, no central lumen, and when it exists it is not only very small, but it has no epithelium. Unfortunately, the species examined by her do not belong to the genera under dispute, with the exception of Megascolides illawarrce, in which the prostate is a " somewhat long and flattened" organ, and has a structure intermediate in some respects between a truly " lobate " gland, such as exists in Megascolex, and a " tubular " gland, such as occurs in Plutellus and others; for the species referred by her to " Megascolides " belong to the genus Plutellus in Michaelsen's sense. If I have dwelt so much 011 the form of the prostate, it is because it seems to me that Michaelsen has not laid sufficient stress upon this organ in shuffling the members of the " Cryptodriline series." It alone, I admit, will not serve for generic distinction; but it may possibly be useful in the formation of subgenera. Dunedin, April 10, 1904. Bibliography. '8 9 . B e d d a r d , F. E. " Oligochfetous Fauna of New Zealand," in Proc. Zool. Soc. p. 377. '90. ------ " Classification and Distribution of Earthworms," in Proc. R. Phys. Soc. Edinb. x. p. 235. '92. ------ " On the Earthworms in the Vienna Museum," in Ann. Mag. Nat. Hist. (ser. 6) ix. p. 113. '93. ------ " Some new and little-known Oligochfeta," in Proc. R. Phys. Soc. Edinb. xii. p. 33. '95. ------ ‘ Monograph of the Oligochfeta.' Oxford. '90. B e n h am , W . B . " An Attempt to Classify Earthworms," in Quart. Journ. Micr. Sci. xxxi. p. 319. '00 (a). ------ " On Acanthodrilus uliginosus," in Trans. N.Z. Inst, xxxiii. p. 125. 00 (6). ------ " On some Earthworms from the Islands around New Zealand," in loc. cit. p. 140. |
