398 
Dr. O. Burger on the 
at the same time a cleft appears on each side between intes- 
tine and parenchyma ( Cerebratulus marginatus and Drepano- 
phorus serraticollis ) . This cleft is interrupted at the points 
at which the extremities of the intestinal cseca come in contact 
with the septa, and also where those plates which include the 
genital sacs and the dorso-ventral muscle-bands touch the 
axial portion of the intestine. This cleft was pronounced by 
Salensky *, w T ho determined its existence in Monopora vivi- 
para and Eupolia aurita , to be a coelom. Salensky finds 
that it is bounded by a somatic and splanchnic membrane. 
The Turbellaria are devoid of cavities of this kind lying 
between the tissue of the body and the intestine. On the 
other hand, muscular septa are present, and in this respect 
the elongated Gunda segmentata f is especially worthy of 
notice, since in it the lateral unbranched intestinal caeca are 
regularly separated from one another in this way. In the 
other direction, however, the pronounced metameric arrange- 
ment of the septa in Nemertines leads us to the Annelids, and 
to the Hirudinese in particular, in which, while a body-cavity 
is non-existent, muscular septa are developed. 
The alimentary canal of the Nemertines exhibits two 
divisions, which are both histologically and morphologically 
well marked off from one another : these are, the fore-gut, 
which is devoid of caeca in all forms, but is lined by a richly 
glandular epithelium, and the mid-gut, which in the two last 
groups is provided with metamerically arranged paired 
evaginations, but is without glands. The intestinal caeca 
decrease gradually in size towards the posterior extremity of 
the animal, and finally we get a little short piece of intestine, 
straight and without glands, which we are able to distinguish 
as rectum, but which nevertheless in the character of its 
epithelial lining does not differ from the mid-gut. It is 
therefore doubtful whether, without referring to embryology, 
we are entitled to speak about a proctodaeum in the case of 
the Nemertines. The mouth is always ventral in Groups I. 
and II., behind or beneath the ganglia, and opens into an 
expanded, bell-shaped, pharyngeal cavity — in the case of 
Group III. in front of the ganglia — which in its turn opens 
into a narrow oesophagus. The mouth does not always open 
independently to the exterior, but more often unites with the 
aperture of the proboscis-sheath. In Monogonopora and also 
in Prosadenoporus the oesophagus opens into the proboscis - 
* Salensky, “ Zur Entwickelungsgeschichte v. Borlasia vivipara Biol. 
Centralbl. ii. Jahrg. 
t A. Lang, “ Der Bau von Gunda segmentata? Mitth. a. d. Zool. 
Station zu Neapel, Bd. iii. 1881. 
