THE GIANT EARTH-WORM OF GIPPSLAND. 51 
n ... ventral nerve cord. 
nn n? ... branches of ventral nerve cord. 
pig ... pigment masses. 
sept sop SSO. 
sept bv ... blood-vessel supplying septum. 
v bu ... ventral blood-vessel. 
y ... cells in diverticulum of tube around dorsal blood-vessel. 
x ... tube surrounding dorsal blood-vessel. 
Fig. 5.—Transverse section through a small portion of the dorsal wall of the 
alimentary canal in the hinder region of the body. Half of the dorsal blood-vessel 
(d. bv.) is represented, and half of the tubular structure (+.) surrounding’ this, 
together with two diverticula (dv.) arising from it. Of these, the upper one is 
almost completely filled with large nucleated cells pressed closely together (y.), with 
strands of connective tissue (cf.) crossing from side to side. The lower one is almost 
empty, though some cells still remain, the others having doubtless passed into the 
tube (v.) Both diverticula open into the tube, and the latter is lined internally and 
externally by cells of the peritoneal epithelium. The walls of the alimentary canal are 
coated internally by columnar epithelium cells, with spherical nuclei (¢f.1) Amongst 
them goblet cells (gob.) are present. The layer of circular muscle fibres is well 
developed, and above and below this is a network of blood-vessels, with connecting 
vessels passing through the muscle layer. More externally lie the longitudinal fibres, 
and outside these again, the cells of the peritoneal epithelium, modified into brown 
cells. These are absent in the mid-dorsal line within the tube (w.), and from them 
long thin processes can be traced through the muscle layers to the epithelium lining 
the alimentary canal. (These processes are finer, and not so clearly marked as in the 
figure.) Hach brown cell has a very distinct spherical nucleus placed where it begins 
to grow narrow. 
Fig. 6.—Section through the modified skin of the clitellar region. The 
epidermic cells pass inwards, and their pointed internal ends lie in a thick 
homogeneous basement membrane. In this lies also a great number of red-brown 
pigment masses, which also pass downwards, surrounding the blood-vessels. Beneath 
the epidermic cells lies a great development of unicellular glands, each of which has a 
swollen internal end, and a narrow tubular part passing upwards towards the 
surface (gl.) Some of the glands are much more swollen than others, and each 
contains a definite nucleus. Amongst them are coiled blood-vessels, and the openings 
of the nephridia (neph.), the inter-cellular part of the ducts of which are very vesicular 
in nature, with extremely thin walls. Amongst the gland cells are pillars of 
connective tissue (ct.), which divide into forks resting upon the circular muscle fibres. 
These pillars surround the nephridial ducts, and are continuous with the basement 
membrane beneath the epidermic cells. 
H 2 
