At the present day feiy groups of the animal kingdom are so well known to the microscopist, few groups present more interesting affinities to the morphologist, and few multicellular animals such a low physiological condition.
As the microscopist usually estimates the resolving power according to the aperture with ordinary day-light, Kohler introduced the " relative resolving power " for ultra-violet light.
Almost every microscopist has had a particular group or type of specimen to which he or she has a special partiality.
With translucent white tentacles, waving like wings in a breeze, they are a wonderful sight to greet the amateur microscopist.