OCR Text |
Show 1900.] NEW SPECIES OF EARTHWORM. 657 also thickened. The next septum is thin and delicate, but curved forwards like those in front. After this the septa are all thin but run straight across the body-cavity. A few strands of muscle bind together some of the thickened septa, but they are not very strongly marked. The alimentary canal is, as in other Benhamia;, furnished with two gizzards. The last of these undoubtedly lies in the sixth segment. The first appears to occupy the fourth segment, two septa intervening between the two gizzards. The gizzards, which are very stout, are pushed back and really overlie and absolutely conceal the spermathecae. Hence the crowding of the septa which immediately follow them. There seems in fact to be more independence between the position of the septa and the intersegmental furrows than is usually the case. The calciferous glands lie in a position which they do not invariably occupy in this genus, i. e. in segments xiv., xv., xvi. They are of a bronzy yellow colour. The intestine does not assume its greatest width until segment xxi. I could find no intestinal caeca such as are sometimes present in the species of this genus. There is a typhlosole in the anterior part of the gut but not posteriorly. Besides a difference in position, that is to say of the segments occupied by these glands, the calciferous pouches differ in certain other points of structure among the species of this large genus. In the present species the surface of the glands is fairly smooth ; the furrowing, seen to so marked a degree for example in Benhamia ccecifera, being practically absent. In transverse sections of the glands they are seen to be somewhat bean-shaped, with a hilum where the duct leaves the gland. On the opposite side there is but one distinct furrow not far from the lower eud of the gland, i. e. that side which is nearest to the oesophagus. The three glands open into the oesophagus by only a single duct on each side. This duct is of considerable calibre, and is ciliated like the oesophagus; it has also muscular walls and is formed of three branches, one from each gland. The glands lie dorsally to the oesophagus for the greater part. The nephridia of all species of Benhamia are of the " diffuse," " plectonephric," or " microuephric " type. Very generally in the description of species this statement has been made without any further additions. In others (as for instance B. octonephra) the more exact arrangement of the nephridial tufts has been noted and has afforded systematic characters. In the present species, there are 10 or 12 nephridial tufts on either side of the nerve-cord, which are rather more conspicuous from the 27th segment or so backwards than they are anteriorly. This is often the case with earthworms, and seems to be due to the peritoneal covering. The micronephridia of this species have a curiously squarish outline. As to tbe vascular sgstem, I have only to observe that the dorsal vessel is single throughout its course and that the last pair of hearts are in segment xiii. Reproductive Organs. The sperm-sacs are large and rather |