It's a glass sculpture, part of a collection of amazingly lifelike glass sea creatures created by Leopold and Rudolph Blaschka in the 1880's. In that era, according to the Design Museum:
Aquaria and natural history museums were then opening all over the world. As the techniques for preserving real plants or creatures were so rudimentary, they needed life-like replicas to exhibit and turned to Leopold Blaschka to provide them. During the 1860s, Leopold supplied glass sea-anenomes to museums, aquaria and private collectors all over Europe. He then added snails and jellyfish to his repertoire and in 1876 received a large order from Londonâ€™s South Kensington Museum (now the Natural History Museum).
By then, Rudolf had joined his father in the workshop, where they worked alone without assistants. Some of their replicas were based on illustrations in natural history books, such as Philip Gosseâ€™s 1853 A Naturalistâ€™s Rambles on the Devonshire Coast and G. B. Sowerbyâ€™s 1857 A Popular History of the Aquarium of Marine and Fresh-Water Animals and Plants. All the early sea-anenomes, for instance, were modelled on such illustrations.
Other replicas were inspired either by the Blaschkasâ€™ own memories of seeing the real creatures - like the first jellyfish which Leopold remembered from a trip to North America - or by copying preserved specimens. In later years, as the Blaschkas became wealthier, they acquired live specimens to work from. These were kept in a specially built aquarium at their Dresden home.