94 
BULLETIN OF THE BUREAU OF FISHERIES 
a close connection between locomotion and the anterior margin of the foot. On 
close examination of this area it was found by the author to be divided by a trans- 
verse depression forming a pair of lips at the front of the pedal surface. Anterior to 
this depression were seen small, irregular, transverse waves, that were too rapid to 
count and to examine carefully, and that never crossed the indentation. These 
waves had also been observed by Parker (1911) and Copeland (1919) in Alectrion. 
The animal creeps forward at an average rate of 2. 6-2. 8 centimeters per minute 
at 26.5° C. — a relatively slow rate — and as in many gastropods reversal of progres- 
sion does not occur. Adhesion depends entirely on the secretion of slime, as is shown 
by the absence of areas of concavity that are necessary if suction plays any part in 
adhesion. 
Microscopic study of the pedal surface showed that the whole of it is covered with 
cilia, and by the use of carmine it was demonstrated that their effective stroke is 
backward. Isolated pieces of the pedal surface showed beating cilia after 24 hours. 
Because the pedal surface is small, it was impossible to repeat Copeland’s (1919) 
observations on Alectrion in which, by allowing the animal to creep along the surface 
of the water, he was able to show that the cilia beat only during locomotion. 
In the study of the natural history of any animal it is important to know some- 
thing about its migrations. If control measures are to be devised this question 
assumes even greater significance since it is so closely related to the distribution of 
the animal. For this reason the migrations of the drill were studied at Hampton 
Roads and at Beaufort. As Gowanloch (1927) found, gastropods are not easily 
marked. After many attempts the following methods were used: (1) Coloring the 
shell with a wax pencil; (2) marking with sealing wax; (3) painting with oil colors; 
and (4) attaching a cerise colored celluloid tag, a method that had serious objections 
but that yielded the best results. The tag was fastened to the outer lip of the shell 
with a fine silver wire. All four methods were used at Hampton Roads; at Beaufort, 
only the celluloid tag. 
At Hampton Roads 577 marked drills were set out over bottoms of various types 
during the year 1927. Because of the depth of the waters those set out over sandy 
and muddy bottoms could not be recovered; only those planted on oyster beds were 
found again. For the recovery of the drills dredging was first used; but, since it 
was impossible to fix the location of the recovered drills and since it did not yield 
satisfactory returns, this method was dropped. The procedure finally adopted was 
as follows: A stake was planted at the desired place, around which the marked drills 
were set. This area was then marked off in concentric circles, 25, 50, 75, 100, 150, 
and 200 feet from the stake. Each circle had from four to six stations which were 
tonged at weekly intervals. It was then possible to know the distance and direction 
of migration. After the first week tonging was done at greater and more scattered 
distances until approximately one month from the time of planting, when collecting 
ceased. 
Table 5. — Results of migrations experiments at Hampton Roads, 1927 
Approximate distance traveled, in feet 
Drills 
recovered 
Time 
after 
planting 
Approximate distance traveled, in feet 
Drills 
recovered 
Time 
after 
planting 
Q 
Number 
2 
9 
Weeks 
2-4 
2-4 
2-4 
75 
Number 
2 
6 
1 
Weeks 
2-4 
2-4 
3 
100_ 
150-200 
