OCR Text |
Show 386 MR. F. E. BEDDARD ON TWO [Apr. 17, replaced by flattened oval vesicles of various sizes, which have much the look of small spermathecae, such as characterize many Greoscolicidae, e. g. Microchceta. The transition is not abrupt, but gradual. By the thirteenth segment, or even a httle before, the transition is accomplished and the nephridial system has the curious appearance indicated in the accompanying drawing (woodcut, fig. 1). When the vesicles are removed separately and examined in glycerine they are seen to be sacs with excessively delicate walls and crammed with cells. These cells are oval to rounded in shape and are sometimes granular, sometimes homogeneous in appearance. In transverse sections these globular sacs were seen to overlie the nephridial tubes. I am of opinion that they are merely an exaggeration of the covering of peritoneal cells, which often take on a glandular appearance and give to the nephridia which they cover a white colour, owing to the granules with which they are laden. The cells are very differently acted upon by the borax carmine which was used as the staining reagent. The homogeneous cells were very deeply stained ; the more granular cells were not at all stained. In these sections the masses appeared oval or circular; at the side nearest to the body-wall were one or two nephridial tubules cut transversely. Alimentary Canal.-As in the last species, there are two stout gizzards in segments v. and vi. The calciferous glands also occupy the same segments as in Millsonia rubens; they are perhaps a little less furrowed and appear to be smaller. The intestine has a moderate typhlosole and also the caeca of the last species. I counted the same number of these and they begin at the same point; their commencement is indicated by the dark pigmentation of the intestine. The posterior set of caeca are rather shorter. Reproductive Organs.-The testes are two pairs of httle white tufted bodies, which lie on the anterior septa of segments x. and xi. The ovaries are rather larger, but occupy an exactly similar position in the xiiith segment. There are three pairs of sperm-sacs in segments xi., xii., xiii. ; they are attached in every case to the anterior walls of their respective segments. Only those of segment xiii. are of any size, and they are not very large. Tbe terminal part of the male efferent apparatus has a very unusual structure. It has been already mentioned that the external pore is single; the internal organs, however, are double, only uniting just at the pore. W h e n the worm is dissected and the intestine removed, two large elevations, one on either side of the nerve-cord, are exposed. Each of these is about five miUimetres long and is quite conspicuous. They are tied down to the parietes by thin straps of muscle, which doubtless serve to retract them after protrusion. The nerve-cord sends to each two nerves on either side, which are the ordinary nerves of the segment. These nerves, instead of coming off at right angles to the cord, run, the anterior pair forwards, the posterior pair backwards. The terminal chamber of the efferent apparatus bears a close resemblance to the |