movements?" asked the biologist, Rastell. "Rats have always migrated."

"I mean nothing of the kind," protested Crawford. "I mean their sudden appearance in a town or a building, their remaining there for a short time and then their sudden disappearance. The folklore and fairy tales are full of that sort of thing."

"That is why I asked you to come to this conference, Mr. Crawford," explained Willowby. "There is something peculiar happening in New York at the present time, and it has to do with rats and their actions. In some way rats of New York seem to be under the control of a set of racketeers who are able to force them to enter any building they select. The rats come and go suddenly. It is all over in a little while, but when they are in the building, they do a lot of damage."

Mr. Crawford interrupted him.

"I doubt if you use the right word, when you say the rats were forced to enter the building. Perhaps you mean that the rats were by some means placed in such a psychic condition that they wanted to enter the building."

"That brings the matter into my field of research," insisted Professor Wilson. "I doubt the fact that they were forced, but if they wanted to, why that brings up all kinds of interesting questions."

"That is what I am after, gentlemen. I simply want to present the problem to you and have you solve it. I personally am satisfied with one thing. These rats are no different than the rats of five thousand years ago. They are just like the rats of classic Greece and imperial Rome. Maybe Mr. Crawford will tell us how they acted."

The antiquarian fairly beamed as he started to ride his favorite hobby-horse.

"Of course, the story everyone thinks of is the one concerning the Piper of Hamelin. It was in the year 1284. The rats were thick, and the Piper agreed to lead them out of the town for a certain sum. He played a pipe, no doubt some kind of flute, and the rats followed him. When the people refused to pay, he returned on the 26th of June, the feast of Saints John and Paul, and again played on the pipe. This time the children, one hundred and thirty in number, followed him into a cave and were lost. The date is well documented. A number of historians believe that it actually occurred, and on the gate of the town is the statement.

"'CENTUM TER DENOS CUM
MAGUS AB URBE PUELLOS
DUXERAT ANTE ANNOS
CCLXXII CONDITA
PORTA FUIT.'[1]

"The same story is found, with variations, in all parts of the world. There is, for example, the story of the wicked Hatto, abbot of Fulda. He was visited by a swarm of rats who killed him. I can give you a dozen variations of that story, but in each of them the rats came and went, suddenly, as Mr. Willowby says they have been doing in New York."

"I should like to see a few examples of this mass movement of rats. I saw a lemming migration in Norway, but that was different," explained Rastell. "It seems to me that if we actually saw one of these nocturnal attacks, we might learn why they wanted to do it."

"He is deadly right," agreed Professor Wilson. "A few actual facts are worth a hundred theories."

"That is why I have asked you to help me," explained the richest man in New York. "I have prepared some experimental stations for your use. I can put you in a grocery warehouse and guarantee that inside of a week you will see more rats than you ever dreamed of. I have a laundry and a small