JOURNAL OF MICROSCOPICAL SCIENCE. 
EXPLANATION OF PLATE XXIII, 
Illustrating Dr. Hubrecht^s Researches on the Nervous 
System of the Nemertines.^^ 
Fig 1. — The brain and the anterior portion of the lateral nerve-chords 
in Ceehratulus^ and the LiNEiDiE in general (Diagrammatic). 
Ar external sheath of nerve-cells is applied to an internal skeleton of 
nerv3-fibre from which latter the principal nerves take their origin. In the 
fig\r*e the fibre is indicated by a lighter tint than the cells. 
7o the right the superior lobe \0) which is coalesced with the inferior 
lolc {U) anteriorly to T is supposed to have been removed. There is a 
thck ventral and a thin dorsal commissure. The median longitudinal nerve 
f/r the proboscidian sheath (js) takes its origin out of the latter commis- 
sure. 
H. Posterior or third brain lobe. N. Nerve-chords. F. Nervus vagus. 
S. Nervous stems to the tip of the snout, the eyes (when present) and the 
muscles of the lateral fissures. 
Figs. 2 — 6. — Different stages of differentiation of the respiratory ciliated 
duct and of the mass of larger cells which are coalesced with the posterior 
brain lobe. This mass of cells is indicated by a lighter tint (in figs. 4, 5, 
and 6) than the mass of darker ganglion-cells. In figs. 2 and 3 the nerve- 
cells do not surround the nerve-fibre, but are applied externally to it ; a 
mass of larger cells is not present here. The ciliated canal and its external 
opening are left white. 
2. Carinella anmlata; 3. Carinella inexpectata; 4. Folia curia; 5. 
Cerebratulus roseus ; 6. Drepanophorus. 
Figs. 7 — II. — The different relative situations of the longitudinal nervc- 
chords in different genera. The epidermoidal tissues are left white, the 
muscles are darker and the nerve-chords of a darker shade still. 
7. Carinella; 8. Cerebratulus; 9. Langia ; 10. Amphiporus ; II. Dre- 
panophorus. 
Fig. 12. — Transverse section (left half) of the oesophageal region of 
Cerebratulus roseus. Neither the epiderm, nor the larger portion of the 
longitudinal muscles have been indicated. 
0. Lumen of the oesophagus; Z. Folds in the mucous membrane; Fr. 
Proboscidian sheath with B, dorsal longitudinal blood-vessel ; L. Thin 
inner layer of longitudinal muscles ; Q. Circular muscular layer ; Z'. Ex- 
terior layer of longitudinal muscles ; M. Median dorsal nerve-cord. iV. 
Left nerve-chord with central fibrous portion separated from the ganglion 
cells by a hyaline sheath. 
Indirect continuous connection with the ganglion cells is a cellular sheath 
encircling the body and situated between the outer longitudinal and the cir- 
cular muscular layers. It is this sheath which the author regards as a 
“ nervous tunic.” 
