THE MICROSCOPE. 199 
as a pulsating canal, serving the double purpose of a heart and 
artery. At v v,is the ventral vessel, also extending the entire 
length, and conveying blood backward. These are connected by 
¢ v, the circular vessels, which at this point are usually two pairs in 
each segment, but break up into finer vessels as they pass downward 
fromdv. At ng, just below the intestine, is the nerve ganglion, 
described later. The most striking peculiarity of this portion of the 
canal is the infolding tph. This is designated the typhlosole. 
The object is plainly to increase the absorbing surface. In the 
specimen from which the drawing was made, the typhlosole has a 
shape differing from that shown in any figure with which I am 
familiar. It is also different from sections taken from other worms. 
Whether the anchor shape is simply an individual peculiarity, or is 
characteristic of some species, is not yet ascertained. It will be 
noticed that at the point where the branches leave the central bar of 
the anchor, there is a blood vessel. From the dorsal vessel there are 
branches running downward into the typhlosole, which break up 
into a capillary net-work, and doubtless communicate with the large 
vessel in the lower part of the typhlosole. 
In Fig. 2, a portion of the alimentary wall is shown more 
highly magnified. At cw, is the internal cuticle, entirely similar to 
the external layer of the body, and continuous with it. The 
epithelial layer ep, differs from the similar layer of the body-wall 
in having larger cells, many of them of a distinctly club shape, and 
all having conspicuous nuclei. These cells appear to be active in 
_the secretion of digestive fluids. At the bases of these cells are 
blood vessels (J b v), forming a loose net-work. Next comes a layer 
of circular muscles (c m), and then scattered bundles of longitudinal 
muscles. Surrounding these is the layer ch, consisting of large, 
pear-shaped cells, which, in fresh specimens, have a greenish tinge. 
These cells cover the entire canal at this point, being most abundant 
- at the dorsal side. ‘They extend down into the typhlosole, and have 
about the blood-vessels a radiate arrangement. As their function is 
not fully understood, they are generally designated as cholagogue 
cells. It seems probable that they at least perform an office 
analogous to the glycogenic function of the liver in higher animals. 
This supposition is strengthened by the arrangement of the cells in 
relation to the blood vessels. 
Fig. 3 represents on an enlarged scale the nerve ganglion 
shown at n g, Fig. 1. One of these ganglia is found in each 
segment, and from them extend two pairs of lateral nerves. They 
are connected with each other by a longitudinal commissure. At 
