No. 3.] SOME NEW FACTS ABOUT THE. HIRUDINEA. 597 
24. A pair of colossal axial nerve-cells are found between 
every two consecutive ganglia in the ventral cord of Branchel- 
fiopsts. The nuclei are very large, and placed about midway 
between the ganglia. The cells stretch from ganglion to gan- 
glion, but do not pass these limits. Between the brain and the 
caudal ganglia there are twenty-two pairs, and in both these 
groups of ganglia the same cells probably occur, for a nucleus, 
resembling in general appearance the nuclei of the axial cells, 
is found imbedded close to the root of each nerve. These axial 
cells undoubtedly correspond to the neurochord cells of other an- 
nelids, and probably to the colossal nerve-fibres of Amphioxus, 
Miiller’s fibres in Petromyzon, and Manthner’s fibres in Ze/eostez. 
Faivre’s intermediate nerve terminates here in the manner de- 
scribed by Hermann for Hzvudo, and has nothing whatever to 
do with the axial cells. Hermann’s “median ganglion-cells”’ 
are also found in this leech. 
25. In Clepsine chelydre, the spinal nerves issue from the 
ventral cord as ¢hvee distinct roots. The anterior, smaller root 
unites with the middle root, at the lateral edge of the ganglia, 
and the two then pass on as one nerve, corresponding to the 
anterior nerve of other leeches. 
26. The agreement in form and structure between Piscicolaria 
and the Japanese Branchelliopsis, is remarkable, for it is much 
closer than that between the fresh-water Pzscicola of Europe 
and marine leeches. Each has ¢hrvee rings to the somite, five 
pairs of testes, and e/even pairs of nephridia. The testes and 
nephridia are in corresponding somites in the two forms. I 
have not thus far succeeded in finding segmental sense-organs 
in Pzscicolarta, but fresh material may bring them to light. 
27. The nephridial organs of Branchelliopsis resemble those 
of Clepsine. Each pair appears to be entirely distinct, and thus 
to present conditions quite unlike the nephridial net-work de- 
scribed by Bourne in Pontobdella and Branchellion. For each 
pair of organs there is a pair of funnels and a pair of external 
pores. The funnel lies in a diverticulum from the posterior 
wall of the segmental sinus, in the angle formed by the junction 
of the segmental with the lateral sinus. A vertical plane cut- 
ting a pair of funnels would divide the first ring of the somite 
into two unequal parts, the posterior of which would be the 
smaller. A horizontal plane would cut the ventral wall of the 
