682 
able manner. That this body has no connection with the true pineal 
stalk has been shown by Goette on embryological grounds, and is now 
further demonstrated by the presence of the newly described superior 
commissure, which, it is true, is small in Rana and Menobranchus, but 
in the Derotremata attains a great size and separates the pineal stalk 
from the plexus by a wide interval. Between the superior and posterior 
commissures in Amphiuma lies a minute flattened sac, composed of a 
single layer of cells resembling those of the ependyma. It rests upon 
the upper brain wall, but without the brain cavity proper. In Meno- 
branchus and Rana, this sac has nearly lost its lumen, and it extends 
forwards above the superior commissure. In all these forms it is com- 
pletely without the brain wall, but in Menopoma the cavity of the sac 
retains by a narrow slit its primitive communication with the true 
brain cavity. These structures are to be regarded as portions of the 
processus pinealis; they lie wholly within the pia mater. I have not 
had an opportunity of verifying Goette’s embryological history of 
the pineal body, but the above features of adult structure so far con- 
firm his conclusions that they show it is a positive error to consider 
the pineal body or its stalk as clearly visible parts of the surface of the 
brain. They show further that the vascular plexus does not form the 
anterior wall of the stalk in the Amphibia, as described by Mihal- 
kovics in the chick, but is an independent structure which has an 
external, not a true resemblance to the pineal body. 
Morphological Laboratory, Princeton, N.J. Sept. 24th 1884. 
6. Über einen Monotus des süfsen Wassers. 
Von Dr. O. Zacharias, Hirschberg i/Schl. 
eingeg. 3. November 1884. 
Es ist bekannt, daß die Turbellarien - Familie der Monotiden 
lediglich marine Formen umfaßt, und daß bisher niemals eine Mono- 
tus-Species im Binnenlande, resp. in süßen Gewässern, angetroffen 
wurde. Dem gegenüber habe ich nun zu berichten, daß die von mir 
im Laufe dieses Sommers angestellte Untersuchung zweier hochge- 
legener Wasserbecken im Riesengebirge die Entdeckung eines un- 
zweifelhaften Süßwasser-Monotus zur Folge gehabt hat. Der be- 
treffende, sehr interessante Strudelwurm hat eine Länge von 3—4mm 
und eine lorbeerblattförmige Gestalt. Unter dem rothbraunen Augen- 
fleck liegt die Gehörblase (Otocyste) mit dem schön glänzenden runden 
Otolithen, welcher deutliche Spuren der für die Monotiden so cha- 
racteristischen »Nebensteinchen« zeigt. Gelappte Dotterstöcke und 
