SOME ABNORMAL ANNELIDS. 443 
occupied by a digestive tract. There is no dorsal blood- 
vessel, but the subintestinal blood-vessel is represented by a 
trunk that pierces all the septa and is traceable to the sub- 
intestinal blood-vessels of the trunk, of which vessel it isa side 
branch. 
The only organ that seems to indicate a digestive tract is a 
peculiar strand of muscles forming a slender cord running the 
whole length of the body-cavity dorsal to the nerve-cord. This 
muscle pierces the septa, and closely accompanies the above- 
mentioned ventral blood-vessel, lying just dorsal to it. It may, 
perhaps, be regarded as a representative of the musculature of 
the digestive tract. 
The body-cavity contains numerous amceboid corpuscles. 
The ventral nerve-cord presents a ganglionic enlargement in 
each somite, and is accompanied by subneural and by lateral 
blood-vessels. Its sheath is but little developed, and its histo- 
logy presents indications of immaturity, though showing the 
normal ganglion cells, giant fibres, and fibrillar substance. 
In such a section the only departures from the normal are 
in the absence of digestive tract and dorsal vessel, in the in- 
complete histological state, and in the presence of a free supra- 
neural muscle-cord. 
A transverse section near the posterior tip, fig. 9, shows 
most of the structures as seen at the middle of the process, 
but the tissues are still less perfected and the ventral blood- 
vessel and its accompanying supra-neural muscle are absent. 
There is in addition at this part of the process a peculiar 
septum dorsal to the nerve-cord, which here is just separating 
from the body-wall. This partition is only the last septum 
much inclined along with the ventral bending of the tip of the 
process, so that it cuts off a small terminal part of the body- 
cavity on the ventral side around the nerve-cord from a larger, 
really more anterior, part that lies dorsally and contains the 
large nephridia. As the nerve-cord sinks down completely 
into the body-wall near the extreme tip of the process, there 
is left above it a small pocket of the body cavity, shut off 
from the rest by the above oblique partition yet open anteriorly 
