Water Cricket Head
This insect might look fearsome but it's only a young Water Cricket. He's a tiny, harmless chap who could comfortably sit on your little fingernail and you'd never notice a thing. They are more properly known as "Hemiptera Velia caprai" and are common to ponds across England.
The slide is dated to 1912 and states that it was produced by Herbert William Hutton Darlaston of Birchfield, Birmingham. This was imaged through a Broadhurst & Clarkson vintage microscope.