OCR Text |
Show 1894.] NEW GENERA OF EARTHWORMS, 389 makes up the greater part of the calciferous gland of Gordiodrilus. Through this tissue pass numerous small blood-vessels of equal calibre, which radiate out from the top of the gland but run parallel through its substance. A single diverticulum from the oesophagus dips down into it, but appears to end caecally and not to be continued on into a few intracellular tubes such as I have described in Gordiodrilus. In the xth and xith segments the oesophagus to some extent retains the structure of the calciferous gland; outside the lining epithelium of the tube is a granular and nucleated mass which is precisely like the glandular mass of the calciferous gland ; outside of this are the muscular layers and the peritoneal covering of the gut; it seems therefore probable that the granular tissue of the calciferous gland is of hypodermic origin and is not formed out of the modification of the peritoneum. The intestine begins in the xiith segment. The nephridia commence in segment v.; they have no muscular end sac. The last heart is in segment xi. The reproductive organs are constituted upon the plan of those of Gordiodrilus, but there are differences of detail. The testes and sperm-duct funnels are in x. and xi. The two sperm-ducts run side by side along the ventral body-wall until about the xvith segment; after this they get to lie in the body-cavity and are to some extent coiled ; they pass back beyond the point where they open on to the exterior, which is no doubt correlated with the protrusible termination of the efferent apparatus. When the worm is dissected the most obvious part-indeed practically the only part to be seen on account of the small size of the w o r m - of the efferent apparatus is a pair of oval or pear-shaped sacs ; these Fig. 3. Male efferent apparatus. a. Spermiducal glands. d. Orifice of one of the spermi-b. Bursa copulatrix. ducal glands. c. Penis. Vji. Sperm-ducts. PROC. ZOOL. SOC.-1894, No. XXVI. 26 |