540 
lateral branches were of unequal size, probably varying with the 
amount of blood contained in them. Numerous other small branches 
penetrated throughout the new tissue. 
The nervous system offers the most important evidence that a 
new head had been regenerated. The development of a cerebral gan- 
elion and two oesophageal commissures connecting it with the nerve 
cord is complete and corresponds exactly with what is found in the 
normal head. A section through one of the commissures is represented 
in fig. 4 Cm. The fifth section in the series beyond fig. 4 is given 
in fig. 5. Here the cerebral ganglion (BR.) is completely separated 
from the ventral nerve cord (NC.) while in the intermediate sections 
the commissure is connected with both the ganglion and the nerve 
cord. Unfortunately the sections pass somewhat diagonally through 
this region, yet the relation of the parts is perfectly evident even in 
this plane. Since, in Allolobophora foetida there are no openings in 
the ventral nerve cord and the only point at which the nervous system 
is penetrated by other organs is where the commissures pass around 
the pharynx, the presence of an opening in the regenerated segments 
gives strong evidence of the development of a brain. A charac- 
teristic feature of the regenerated brain, which should be noted in 
this connection, is, as in the normal worm, the presence of large 
ganglion cells surrounding both the cerebral ganglion and the pharyn- 
geal commissures, in contrast to the ventral nerve cord which has 
ganglion cells on the ventral side only. 
