STUDIES OF THE OYSTER DRILL 
101 
fish, spots, croakers, oyster drills, and Crepidula were placed at one end of a tank of 
areated sea water. The water was not permitted to run in these tanks because of 
the effect of currents on the movements of the drills (Federighi, 1929). At varying 
distances tagged drills were introduced and their movements noted. Although no 
results were obtained as regards the greatest distance at which the drills react to the 
foods some data were collected on the relative efficiency of the various meats. It 
was found that oyster meat is preferred to any other, and mollusks are preferred to 
fishes. In one of the experiments there was introduced besides the various meats 
some oyster spat. The result was that the drills attacked these shelled oysters in 
preference to the more easily available meats. It is true that not all the drills went 
to the shelled oyster spat, but a good number did and this in spite of the fact that 
they had to pass by some freshly killed oyster meat to get to them. 
BREEDING HABITS 
In Urosalpinx cinerea as in other prosobranchs the sexes are separate, the males 
being distinguished by a large curved penis which lies at the right side of the head 
behind the eyes. The two sexes can also be separated by macroscopic examination 
of the gonads, the male glands being whitish in appearance; that of the female yellow 
to orange in color. The eggs are laid in small, yellow membranous, vaselike cap- 
sules attached to the substratum by a solid expanded foot. The egg case is flattened 
vertically with edges marked by keellike ridges and has, at the top, a small cap 
through which the fully grown larvae escape. Within the capsule is a soft jelly like 
fluid in which the eggs are laid and which serves not only to protect them from 
mechanical injury but also as a source of food. At Hampton Roads during 1927 the 
first egg cases were collected in the field on May 20 and in the laboratory on May 19, 
while at Beaufort the first egg cases were gathered (during 1928) on March 21, and 
in the laboratory on March 30. Spawning continued throughout the summer, and 
during the fall it gradually decreased in intensity until at Hampton Roads spawning 
practically had ceased by the 1st of October. 
The details of spawning, development, and hatching were studied in the labora- 
tory. The work included observations on the following subjects: (1) Copulation; 
(2) behavior of the female during spawning; (3) the number of times a single female 
spawns during one season; (4) duration of oviposition; (5) the rate of oviposition; 
(6) the number of egg cases laid per female; (7) the number of eggs per egg case; 
(8) duration of the incubation period; and (9) the percentage of drills hatched. 
Although copulation undoubtedly occurs in TJrosalpinx cinerea, copulating drills 
were never collected in the field nor was copulation ever observed in the laboratory — 
a fact probably explainable by assuming that copulation occurs only at night. For 
this reason it is not known whether the drill copulates more than once a season or 
whether the sperm are carried over from year to year. 
Because of the snail’s negative geotropism the female creeps up to the higher 
levels to spawn. Without this response the eggs would be laid in the lower strata 
and be suffocated and buried in the mud. In almost all cases if oysters were present 
in the tank the female would climb on them to deposit the capsules in preference to 
the sides of the tank. While spawning the female does not feed but remains attached 
to the substratum and unless disturbed continues until spawning is completed. Ob- 
servations in the laboratory show that each snail spawns only once during the summer, 
although in some cases, when the animal was disturbed while spawning, it would 
cease, move away, and for several days show no spawning activities. After a few 
