Anatomy and Histology of Nemer tines. 399 
sheath — in the latter case at some distance from its exterior 
aperture. The same thing very probably occurs in Geone- 
mertes palaensis, only in this case the opening of the alimentary 
canal is carried right to the anterior extremity, so that, as a 
matter of fact, the apertures of mouth and proboscis coincide. 
In Malacobdella , however, the proboscis-sheath opens into a 
peculiar cavity, which is provided with villi, and must be 
regarded as a veritable pharynx. Yon Kennel* * * § would have 
us believe that the cavity of the proboscis-sheath opens into 
the mouth in Geonemertes palaensis also ; but it appears to 
me, according to the figure which the author gives, that the 
condition is precisely the same as in Monogonopora and 
Prosadenoporus , that is to say that the oesophagus opens into 
the most anterior portion of the cavity of the proboscis-sheath. 
The anus, which is never absent, is always terminal. 
Yon Graff f, too, asserts that the proboscis-sheath in Geo - 
nemertes chalicophora opens into the mouth. But on referring 
to Taf. xx vi. fig. 7, of the work in question, we see quite 
clearly that the oesophagus opens into the proboscis-sheath at 
a considerable distance from the external aperture of the 
latter ; it curves distinctly upwards , and the opening of the 
proboscis — of the mouth according to von Graff — is almost 
exactly terminal in this form, whereas it should be ventral if 
it were the mouth-opening. In all respects the structure 
presents the appearance of a prolongation of the proboscis- 
sheath. 
In the intestine of the Nemertine we have the type of that 
of the Annelid. If, however, we attempt a comparison with 
the intestinal tract of a Turbellarian, even though we select 
Gunda segmentata for the purpose — a form distinguished by 
the possession of a straight unbranched intestine, which is 
provided with a regular series of csecal evaginations and opens 
into a mouth placed at the extreme anterior end of the body 
— we nevertheless unavoidably fail ; for the intestine of our 
Turbellarian, however far it may have diverged in develop- 
ment from the radially-branched organ of the Polyclad, in the 
direction of that of the Nemertine, is devoid of an anus. 
According to Hubrecht } and Max Muller § the proboscis 
* Von Kennel, u Beitrage zur Kenntnis der Nemertinen,” Arbeiten aus 
dem Zool. Inst, zu Wurzburg, Bd. iv. 1877. 
t Von Graff, “ Geonemertes chalicophora , eine neue Land-nemertine,” 
Morphol. Jahrb. Bd. v. 1879. 
X Hubrecht, ‘ Report of the Scientific Results of the Voyage of 
H.M.S. 4 Challenger,’ 1873-1876,’ Zool. vol. xix. Nemertea, 1887/ 
§ Max Muller, 4 Observationes Anatomicse de Vermibus quibusdam 
maritimis,’ Berolini, 1852. 
