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Show 1 9 0 5 .] NEW ENCHYTR.'EID WORM. 5 6 3 The dorsal blood-vessel is anteclitellian in origin and does notseem to be connected at its point of origin with any dorsal diverticulum of the gut such as exists in Buchholtzia. It arises in the xitli segment. I could see no " heart body." The exact origin of the dorsal vessel is rather difficult to locate exactly in this very minute Enchytrseid. I fix the xith segment as the point of emergence from the intestinal plexus, since the vessel is very much broader here than in the dorsal region of the blood-plexus posteriorly * and stands out more from the walls of the gut. The vessel is, in fact, in this segment quite twice the width that it is anteriorly to the point in question. Commonly, for example in llenlea nasuta, the dorsal vessel is much wider at its emergence from the intestinal plexus than it is anteriorly. This is confirmed by an examination of a series of transverse sections, from which it was evident that the dorsal vessel stood away from the walls of the intestine in the anterior part of the clitellum ; it was indistinguishable posteriorly. Concerning the reproductive organs, it may be observed, in the first instance, that the position of the various ducts and pouches is perfectly normal. The external orifices of the atria are very conspicuous upon the ventral surface of the twelfth segment, in line or nearly so with the ventral seta1 of that segment. These set* are, however, absent, and there are no penial set* of any kind. The testes and the ovaries occupy their usual segments, 1. e. xi. and xii. Concerning the exact form of the sperm-duct funnel I am unable to give details ; but I have identified them and satisfied myself that they are of the usual Enchytrseid pattern. The spermathecse offer characters of obvious systematic use. They open on the one hand into the oesophagus in the fifth segment, and on the other by a muscular duct on to the line dividing segments iv. and v. I could not find any diverticula. There are but a single pair of spermathecse. In the above description 1 have only been able to dwell upon a certain number of facts which are of systematic importance in the group. Of importance in determining the genus are : (1 ) the presence of four bundles of curved set* on all the segments of the body, save the first and the twelfth ; (2) intraclitellian origin of dorsal vessel ; (3) absence of any diverticula to oesophagus ; (4) simplicity of spermathec* and their communication with oesophagus. Of the thirteen genera allowed by Micliaelsen f, 9, viz., Achcela, Michaelsena, Mesenchytrceus, Chirodrilus, Buchholtzia, Enchytrceus, Stercutus, J\lariont7ia,, and Lumhricillus, aie excluded by these characters. Though I did not find any dorsal pores, it is clear * It must be borne in mind that Pierantoni (" Studii anatomici su Michaelsena macrochceta Pierant.," Mitth. Zool. St. Neapel, xvi. 1903, p. 409) traces a distinct dorsal vessel in the intestinal plexus posteriorly to the region where the former is said to commence. Bat this does not affect the point of emergence, f Oligochseta, in ‘ Das Thierreich' (Berlin, 1900). |