108 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
being thus stimulated; for, when an actinian was cut transversely in 
two, the portion without tentacles still took in meat but refused sand 
and paper (Loeb, ’91, pp. 69, 70). 
In the year following that in which Loeb’s publication appeared, Nagel 
(92, p. 335) described some experiments on what he called the sense 
of taste in actinians. His work was done apparently without knowledge 
of the results obtained by Loeb, for he makes no mention of these. 
This oversight was probably due to the fact that Loeb’s studies appeared 
as a separately published pamphlet, under the title “‘ Untersuchungen 
zur physiologischen Morphologie der Thiere,” which would not lead 
one to suspect that it contained matter of importance on the stimula- 
tion of actinians by their food. 
Nagel’s observations were made on a number of actinians, especially 
on representatives of the genera Adamsia and Anemonia, and led to the 
conclusion that the only part of the actinian capable of being stimu- 
lated by the soluble constituents of the food was the tentacles. This 
result was abundantly confirmed by Nagel’s (94°, pp. 528 and 531) later 
observations, in which he showed that even when a piece of meat was 
placed upon the lips of an actinian, no response followed, and he be- 
lieved that the animal might even die of hunger with the food at its 
mouth, provided the juices from this food did not reach and stimulate 
its tentacles. 
Thus Nagel believed that the tentacles were the only part of the 
body capable of being stimulated by food, whereas Loeb concluded that, 
in addition to the tentacles, other parts of the body could thus be 
stimulated. 
Another difference exists between the views of these two investigators. 
Nagel (’94", p. 539), in his description of the way in which the food is 
transported to the mouth and swallowed, mentions only muscular 
action. Loeb (’95, p. 419), on the other hand, believes that, in addition 
to the muscles, the ciliated surfaces play an important part in moving 
the food. 
To what extent these different opinions are supported by the con- 
ditions in Metridium will be seen from the following account. 
Gross Anatomy of Metridium. — In the common actinian of our coast, 
Metridium marginatum Milne-Edwards, the aboral disk is broadly ex- 
panded and is more or less permanently attached to some fixed object 
in the water. The considerable column which rises from the aboral 
disk may in a large, fully expanded animal reach the height of several 
inches. The column ends above in a complicated oral disk, which con- 
