Where's Professor Snape? shouted a girl from the Slytherin table. He has, to use the common phrase, done a bunk, replied Professor McGonagall, and a great cheer erupted from the Gryffindors, Hufflepuffs, and Ravenclaws.

After the completion of copulation, the number of eupyrene sperm bundles in a spermatophore gradually decreased.

This seemed to be an inexpugnable refuge, where we could live untroubled and learn to know each other."

Because this sentence makes a statement, a period is the appropriate endmark.