"How do the oystermen fight them?"
"By catching them in tangles. The snarled cotton waste does no harm to the oyster, but, as it is pulled over the bed, picks up hundreds of starfish and sea-urchins. Up-to-date vessels engaged in that work have a vat of boiling water on deck, into which the tangle is plunged when it is pulled up from the bottom. This kills the starfish and is a great gain over the old system of picking them out of the tangle by hand.
"But the worst of all the oyster's enemies," the director continued, "and the one on which I am working, is the oyster-drill. At least eighty per cent of the possible oyster crop is destroyed by this sea-snail. This creature, usually about half an inch long, crawls on an oyster—usually a young one—and with a rasp-like tongue files a hole in the shell, through which it sucks the juices out of the oyster. The only thing that keeps the oyster-drill in check at all is that as soon as it is big enough for a younger drill to climb on its shell, it is apt to suffer the same fate. It is a case of reversed cannibalism, the stronger falling to the weaker."
"What can be done to stop it?"
"Nothing so far," said the director; "that is my chosen problem. Because the drill prefers the thin-shelled mussel to the thicker-shelled oyster it has been suggested that mussels should be planted outside oyster-beds, so that the drills would stay there. But the cure would be worse than the disease, for the mussels would spread over the oyster-bed and the drills with them, since they would have so excellent a breeding ground. No, the problem is still unsolved, and the people of the United States are looking to the Bureau of
Fisheries to solve it. The Bureau has given it to me. That's the fascination of this work, that on your own toil and your own skill and ingenuity a factor of world-wide importance may depend."
"Perhaps——"
"What is it, Colin?"
"It just occurred to me, sir," the boy answered, "that perhaps some parasite which would prey on the drill might be found."