OLFACTORY REACTIONS OF MARINE SNAILS 209 
The osphradium of Busycon is an elongated organ slightly over 
three centimeters in length, broadest in the middle and tapering 
at both ends. It possesses a longitudinal axis bordered on both 
sides by a series of pigmented leaf-like structures, which give 
it the superficial appearance of a gill. In this bipectinate type 
of osphradium the axis is described as an elongated ganglion 
from which nerves pass off laterally to their terminations in the 
lamellae. The exact nature of the nerve endings is disputed. 
It was first necessary to find a method for rendering the 
osphradium functionless. It proved to be a very difficult task, 
principally on account of the inaccessibility of the organ. Since 
handling of the animal caused more or less contraction of the 
soft parts, the snail had to be anaesthetized before the osphradium 
could be reached at all. A concentrated solution of magnesium 
sulphate in sea water proved to be an excellent anaesthetic for 
the purpose, as the snails recovered quickly without showing 
any ill effects. The usual method was to place the animal in 
the solution in the late afternoon or early evening, where it 
remained over night. The following morning the operation was 
performed and the snail returned to an aquarium supplied with 
running water. It usually became more or less active in several 
hours and was in condition for study the next day. The olfac- 
tory reactions of the snails were always tested before operating, 
and only those which showed vigorous responses were selected for 
further experimentation. 
Attempts to eliminate the osphradium were first made by 
scraping it, burning it with a heated platinum wire, or by com- 
bining the two methods. Since the elongated organ follows the 
curvature of the shell, and only about one-half of it can be seen 
under the most favorable conditions, the task of destroying the 
deeper portion was largely one of guesswork. The mantle in the 
vicinity of the osphradium being extremely thin, was easily 
punctured, or was apt to break through after the operation. 
When this happened the snail often contracted the mantle and 
siphon, and accordingly was in poor condition for subsequent 
tests. A number of individuals, however, recovered from the 
operation with mantle and siphon externally normal in appear- 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 25, No.1 
