Another near relative of the two animals we have just described is the sea slug or sea cucumber. Though an article of commerce of some importance in the far East, the sea slug is not so common on our coasts as its relations. We must make a point of finding a specimen, however, for it provides us with one of the most remarkable objects for our microscope that could possibly be imagined. One species, which goes by the name of _Synapta Inhærens_, is the one most worthy of examination. We must describe the creature first of all so that we may know what to look for. It is aptly named sea cucumber for it is not unlike that fruit--yes! fruit is correct, though the cucumber is more often called a vegetable. The animal’s skin is tough and leathery and at the head end there is a fringe of feathery tentacles. The sea cucumber must be looked for amongst sea weeds or, maybe, he lies buried in the sand, with only his fringe of tentacles on view. A friendly fisherman will probably aid us in our search. Having found our creature we must examine his leathery skin under the microscope. To the touch it is evident that it is studded with some flinty matter, but the microscope alone can show us the amazing beauty of this armour. Under a low magnification, we can see, dotted over the leathery skin, some nearly circular plates to each of which is attached a little anchor. Now, from a dead animal of course, we must scrape away some of these objects and examine them with a higher magnification. Even the hardened microscopist will be delighted when he sees the armour of the sea cucumber for the first time. Each anchor is hinged to a little plate, each little plate, nearly circular in outline, is perforated with seven holes, six round the circumference and one in the centre and every perforation has a toothed margin. So perfect are these minute plates and anchors, that the most intricate man-made machinery could not have turned them out more perfectly to pattern. They are precisely similar to one another in size and shape; as objects for the microscope, even the sea with all its store of wonders, can offer us nothing more marvellous.