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Show 1901.] ON THE STRUCTURE AND ARRANGEMENT OF EARTHWORMS. 187 supplied a sense-organ of the supraorbital canal and sent a few twigs to the surrounding skin. This somewhat complicated description when compared with the figure will, I trust, make it clear that these two supraorbital sense-organs in Chimcera do not, as was supposed, present an anomaly in their innervation, but receive their nerves in all likelihood from the superficialis as do the other organs of that canal, and in their mode of innervation show a close similarity to those that lie in front of them ; for in both cases the actual nerve-truuk from which the filaments for the individual sense-organs arise is of a compound nature formed by an intimate blending of the superficialis VII with the profundus V, differing only in the fact that in the case of these two sense-organs the union occurs between the smaller branches of the nerves, while in that of the organs in front it involves their main trunks. In both cases the fusion is so complete, that it is impossible by simple dissection to say definitely that the fibres derived from the superficialis terminate in the lateral-line sense-organs, while those of the profundus are distributed to the skin ; but the probabilities that such is the case, are so great as to almost amount to certainty. 3. Contributions to the Knowledge of the Structure and Systematic Arrangement of Earthworms. By F R A N K E. BEDDARD, M.A., F.R.S. [Received January 31, 190.1.] (Text-figures 50-58.) 1. On Polytoreutus gregorianus. This species was very briefly defined by me five years ago in m y Monograph of the Oligochaeta l. Since then the publication of descriptions and illustrations of various new species of the genus has decided m e to attempt an addition to our knowledge of this remarkable genus by a fuller account of the form which I named after Prof. Gregory of Melbourne, and which was collected by him in Africa during his expedition of 1891. The worm measures 230 m m . in length by a diameter of 9 m m . The number of segments are between four and five hundred2. As might be supposed from their large numbers, the segments are very short; this is the case with all those lying behind the clitellum; those forming the clitellum aud those lying in front of it are stout segments as in other earthworms. The setce, as in other species of Polytoreutus, are in couples, of which the two lateral are more closely approximated to each other than the two ventral. The disproportion of the spaces separating the two lateral seta? from each other and the two ventral setae is 1 Oxford, Clarendon Press, 1895, p. 612. 2 These measurements differ slightly from those which I originally gave. |
