178 MANTON COPELAND 
literature devoted to mollusks contains numerous references to 
these gasteropods congregating in great numbers about dead 
animals, and several observers have described buried snails 
coming out of the sand when food was placed in the water near 
them. This ability of the carnivorous snails to find food has 
quite generally been attributed to a well developed sense of 
smell, but very little definite information concerning their 
olfactory reactions and organs appears to have been obtained 
by experimental methods. Most recent writers in discussing 
the sense of smell in this group refer to the work of Nagel (’94), 
whose studies on marine gasteropods however were evidently 
limited, and who, by stimulating them with strong or irritating 
substances, used stimuli which were inappropriate for calling 
forth olfactory reactions, at least so they could be distinguished 
from other types of chemical responses. Accordingly an experi- 
mental investigation of olfaction in two species of snails was 
undertaken in view of determining particularly the sensitiveness 
of the animals and the characteristics of their responses to 
olfactory stimuli, whether they are directed to food or find it_ 
by random movements, and the location of the receptors con- 
cerned in the reactions. 
A part of the work was carried on at the United States Fisher- 
ies Biological Station at Woods Hole, and I wish to express my 
gratitude to the resident Director, Dr. P. H. Mitchell, for many 
favors received during my stay. 
II. EXPERIMENTS 
ALECTRION OBSOLETA 
An investigation of olfaction in marine gasteropods was begun 
by a study of the food reactions of the mud snail, Alectrion 
obsoleta (Say), formerly included under the genus Nassa or 
Ilyanassa. It is a rather small species, the expended foot 
measuring from fifteen to eighteen millimeters in length, and 
about ten millimeters in width in its broadest part. The an- 
terior border of the foot is extended on both sides so as to pro- 
duce recurved processes, approximately one millimeter long, 
