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PRESIDENT S ADDRESS. 
taken from Dr. Schiemenz’ paper, have considerable interest, not 
only from their practical importance, but as helping in the elucida- 
tion of the inter-relations between different organisms, and in 
giving some idea as to the functional importance of certain details 
in their structure. Schiemenz finds that Starfishes attack Molluscs 
in one of two ways. The first case is exemplified by Astropecten 
aurantiacus, which lives in sand, in which it pursues its prey. The 
Molluscs (Bivalves and Gasteropods) are pushed by its tube-feet 
into its mouth, which can he dilated to a surprising extent ; and 
digestion takes place inside the stomach. One of the Gasteropods 
which lives in sand with Astropecten is Natica (Neverita) josephinia, 
a species which itself attacks bivalves, boring neat round holes in 
their shells by means of a gland which secretes an acid, probably 
sulphuric acid.* N. josephinia has a peculiarity, shared to a less 
extent by certain other species of the same genus, of being able 
to cover its shell with a lobe of its foot. 
The fact that many Molluscs cover their shells, temporarily or 
permanently, with various parts of their soft bodies is one for 
which an explanation is needed, seeing that the shell of a Mollusc 
is presumably for the protection of the soft tissues. In this case 
it appears that the covering of the shell is a distinct protection 
against the attacks of Starfishes, as was shown by observing the 
way in which Asterias (jlacialis attacks the Natica. If the latter is 
crawling about, with its foot protruded, contact with a Starfish 
at once results in the shell-lobe being closed over the shell. If 
the Natica is retracted into its shell when it is attacked by the 
Starfish, a conflict ensues. The Starfish attempts to devour the 
Mollusc, which in its turn endeavours to protrude its foot from its 
shell. If the Starfish cannot prevent this, the foot swells up by 
taking in water, and it is then drawn tightly over the outer 
surface of the shell, thereby sweeping off all the suckers of the 
tube-feet of the Starfish, which are unable to attach themselves to 
the slippery soft tissues of the Mollusc, with which the victory 
remains. 
A different result ensues in the event of the Starfish attacking 
* Schiemenz, “ Wie bohrt Natica die Muscheln an ? ” Mitth. Zool. Stat. 
Neapel, vol. x., 1801-93, p. 153. 
