596 WAITMAN. (Vor. ar 
ganglia standing at regular intervals apart. There are gener- 
ally seven pairs of distinct spinal nerves arising from the caudal 
ganglia, and sometimes eight. 
20. The postoral (infra-pharyngeal) ganglia represent five 
somites, as can be shown in Clepsine parasitica and Branchelli- 
opsts. Whether one or more somites are represented in the 
pre-oral (supra-pharyngeal) ganglia, I am not prepared to say. 
As there are always twenty-one ganglia between the pharyngeal 
and caudal groups, we have thirty-three somites represented in the 
ventral chain (exclusive of the pre-oral ganglia). 
21. A careful analysis of the annular composition of the body 
of Clepsine has enabled me to find just ¢zwenty-szx somites in 
front of the caudal sucker. Adding seven for the sucker, we 
have thirty-three, which makes the number of somites deter- 
mined by the external rings agree precisely with the number of 
ganglia in the ventral chain. 
22. The assertion by Mr. Apathy that there are szr caudal 
ganglia lacks ove of being true; and his statement that there 
are always three anal ganglia would hit the mark in very few 
cases indeed. Mr. A. boldly asserts that there are szx somites 
represented in the pharyngeal ganglia. This author does not 
appear to be aware that the nice balance which he strikes be- 
tween the head and the tail of a leech is open to any serious 
objection. For the present I pursue the criticism no further. 
23. The nervous system of Branchelliopsis presents one fea- 
ture of exceptional interest. This leech possesses veritable spzxal 
ganglia. These ganglia are lodged in the anterior (sensory) of 
the two spinal nerves of each somite, at a short distance from 
the ventral cord. The two nerves issue side by side, but di- 
verge after passing the ganglia of the ventral cord, and then are 
re-united by a commissure, at the level of the spinal ganglion. 
Passing the spinal ganglion, the nerves at once subdivide into 
several branches. One of the main sensory branches runs out- 
ward in the anterior wall of the segmental sinus, while another 
large branch (motor ?) runs in the dorsal and posterior wall of 
the sinus. The pre-sinal branch divides just before reaching 
the longitudinal muscles, into three branches, the smallest of 
which appears to end in the muscles, while the two remaining 
pass on, one to the anterior, the other to the posterior side of 
the lateral heart, and eventually end in segmental sense-organs. 
