OCR Text |
Show 1899.] ON TWO EARTHWORMS. 809 extending from the 26th to the 31st segment. The modification of the integument, however, is only ventral: it does not die away gradually, and there is a sharp demarcation from the dorsal surface which is unmodified. The boundaries of the segments could be noticed with perfect ease in this region. The setae, however, were not obvious. Another external feature of some little importance, which was observed, is the presence of papillae. They are situated ventraily, but are not perfectly symmetrical iu their arrangement, inasmuch as they correspond to setae which are themselves in this species scattered after the fashion of Pontoscolex and some other Geosco-lecids. Of these papillae there are 4 on each of segments xi., xii., xxiii., xxiv., and 2 on each of segments xxxi., xxxii. They are oval in form, the long axis coinciding with the transverse diameter of the body ; the middle of each is higher than the periphery. These papillae were naturally plainer upon the mature than upon the immature examples. The setae which lie in the middle of the areas formed by these papillae are larger than those elsewhere, but do not appear to present any marked difference of form. We should add that the spiny tip of the setae, on account of which the generic name was first bestowed, is not always perfectly obvious ; but this may be very likely due to wear and tear. As to internal characters, the main addition that we have to make to the original description concerns the sperm-sac. In the original non-mature example these, though long, only occupied 15 or 20 segments. In an immature example from tbe material now before us the sperm-sac passed back to as far as the 90fch segment; in a mature example much farther, to the 119th. They thus occupy in the latter case no less than 109 segments. Their structure is thus : in segment xi. the sac commences with a dilated pouch, flatfish, bigger ventraily than dorsally ; in the next segment they are thinned down to a fine thread-like tube attached to the lateral walls of the intestine. About segment xxxiii. the sac dilates into a string of irregular-shaped sacs arranged without any regard to segmentation. Somewhere about segment lxxv. these irregular sacs bear numerous processes, as was figured in the paper in the ' Quarterly Journal of Microscopical Science ' already referred to. There are six thickened septa lying behind the gizzard (which is in segment vi.). No calciferous glands were seen. W e should add that the mature worm is larger than the originally described immature example. One of ours measured 113 m m . by 5 m m . in diameter. |