The Nudibranchs owe their prominence in British zoology to the late Dr Johnston of Berwick, and to the splendid monograph of Messrs Alder and Hancock.

Inhabitants for the most part of the laminarian and littoral zones, the rocks and rock-pools, by minute and continued search, produced the greater number of those met with at St Andrews, the few others being procured from fishing-boats and debris of storms. Almost all require to be sought for with care, and generally escape superficial notice altogether. Most have been kept for a longer or shorter period in confinement, and some are living even now, though with greatly diminished bodies, and less brilliant tints, the results of insufficient food and other unfavourable circumstances.