112 E. RAY LANKESTER, ON THE 
entirely fibrous, and consists of a broad, transverse, com- 
missural band, derived from the pharyngeal collar, and of 
fibres from the roots of the cephalic nerves. Each crus of 
the collar enters its lobe on the under side. Some of its 
fibres curve backwards to the convex vesicular mass ; others 
ascend to, perhaps partly terminate in, the cells near the 
roots of the cephalic nerves, and the rest cross transversely, as 
the broad band, to be continuous in front of the notch with 
that of the opposite ganglion. 
The supra-intestinal chain of ganglia, when placed under a 
4th objective, displays a remarkable structure. The under 
’ surface of the entire chain—cords as well as ganglia—is 
covered with a lamina of round, oval, and pyriform cells, and 
on its upper surface a row of cells of the same kind is found 
along each border. At every point of communication between 
the branches which form the plexus a minute ganglionic en- 
largement is seen, from which new branches proceed to form 
other enlargements of the same kind. As the plexus extends 
from the chain the ganglionic points diminish in size, while 
the smaller branches given off from the trunks increase in 
number, and communicate like a capillary network. The 
ganglia of the subventral chain have their vesicular substance 
on the under surface, and consist of about two strata of cells 
continuous in a lamina across both cords. Along their 
borders, however, the cells form a thicker layer or column, 
which extends for some distance along the intervening cords. 
In form and general appearance the cells are similar to those 
of the pharyngeal chain, but many of them are larger. Within 
the ganglia the roots of the nerves diverge in three different 
ways—1], longitudinally; 2, transversely ; and 3, to the gray 
or vesicular substance. The first, or longitudinal, form a 
large portion of the nerves, and run in equal numbers in both 
directions, backwards and forwards, along the whole length of 
the corresponding cord. In their course some of them near 
the border separate in succession from the rest and enter the 
lateral column of cells; others proceed as far as the next nerve, 
with the roots of which they form loops, and pass out, while 
the rest continue onwards and, perhaps, in successicn form 
similar loops with distant nerves. Mr. Lockhart Clarke has 
shown that the same kind of arrangement exists in man and 
the mammalia as well as here. The second order of fibres 
are less numerous and, in general, less distinct than the rest. 
They proceed from the middle of each opposite root, and cross 
the cords directly. The third order of fibres are those dis- 
tributed to the vesicular substance. Mr. Clarke was not 
able, after repeated examinations with the microscope, to trace 
