Tom, much perturbed at these tidings, was feverishly endeavouring to extract some little information from his companion concerning the compound, when a bell rang abruptly inside the room and a janitor with a red face and a blue slip of paper appeared at the door.

“Dillon, Dimsdale, Douglas,” this functionary shouted in a very pompous voice, and three unhappy young men filed through the half-opened door into the solemn hall beyond.

The scene inside was not calculated to put them at their ease.  Three tables, half a dozen yards from each other, were littered with various specimens and scientific instruments, and behind each sat two elderly gentlemen, stern-faced and critical.  At one side were stuffed specimens of various small beasts, numerous skeletons and skulls, large jars containing fish and reptiles preserved in spirits of wine, jawbones with great teeth which grinned savagely at the unfortunate candidate, and numerous other zoological relics.  The second table was heaped over with a blaze of gorgeous orchids and tropical plants, which looked strangely out of place in the great bleak room.  A row of microscopes bristled along the edge.  The third was the most appalling of all, for it was bare with the exception of several sheets of paper and a pencil.  Chemistry was the most dangerous of the many traps set to ensnare the unwary student.

“Dillon—­botany; Dimsdale—­zoology; Douglas—­chemistry,” the janitor shouted once more, and the candidates moved in front of the respective tables.  Tom found himself facing a great spider crab, which appeared to be regarding him with a most malignant expression upon its crustacean features.  Behind the crab sat a little professor, whose projecting eyes and crooked arms gave him such a resemblance to the creature in front that the student could not help smiling.

“Sir,” said a tall, clean-shaven man at the other end of the table, “be serious.  This is no time for levity.”

Tom’s expression after that would have made the fortune of a mute.

“What is this?” asked the little professor, handing a small round object to the candidate.

“It is an echinus—­a sea-urchin,” Tom said triumphantly.

“Have they any circulation?” asked the other examiner.

“A water vascular system.”

“Describe it.”

Tom started off fluently, but it was no part of the policy of the examiners to allow him to waste the fifteen minutes allotted them in expatiating upon what he knew well.  They interrupted him after a few sentences.

“How does this creature walk?” asked the crab-like one.

“By means of long tubes which it projects at pleasure.”

“How do the tubes enable the creature to walk?”

“They have suckers on them.”

“What are the suckers like?”

“They are round hollow discs.”

“Are you sure they are round?” asked the other sharply.