NATURAL HISTORY — ZOOLOGY. 229 



spinous arms, was secured in situ on the rope, and consigned to a 

 bottle of spirits. 



The great natural history fact of the Expedition is, that at a depth 

 of two miles below the surface, where the pressure must amount, at 

 least, to a ton and a half on the square inch, and where it is difficult 

 to conceive that the most attenuated ray of light can penetrate, we 

 capture a highly organized species of radiate animal, living, with its 

 red and light pink tints as clear and brilliant as in its congeners 

 which dwell in shallow and comparatively sunshiny waters. Where 

 one form so highly organized has been met with, it is only reason- 

 able to assume that other correlated forms may also exist. Hence 

 we may look forward to the discovery of a new submarine fauna in- 

 habiting the deeper zones of the ocean. 



The law will eventually be found to hold good, according to Dr. 

 Wallich, that "any marine animal, within the cellular structure 

 of which air or any other gaseous fluid does not necessarily occur in 

 a free state, and every portion of whose organization is permeable 

 by fluids, either through capillary or endosmotic and exosmotic 

 agency, may exist under the extraordinary pressure present at great 

 depths." — See Dr. Wallich's Notes, together with "Observations on 

 the Nature of the Sea-bed, as bearing on Submarine Telegraphy," 

 published by Taylor and Francis. 



STRUCTURE OF PEARL. 



Mr. Andrew Bryson has read to the Royal Physical Society a 

 paper upon this interesting subject. We pass over the early history 

 of Pearls, and come to that of the gems in our own time. 



Mr. Bryson remarked that, though the French are now by far the 

 most successful producers of artificial pearls, he had failed to obtain 

 the slightest hint of the method employed, no paper having appeared, 

 as far as he was aware, on the subject. The only notice of the 

 formation of the coques de juries of the French which he had obtained 

 was by Von Siebald, who has given, in his Zeitsclirift fur Wis- 

 senschaftliche Zoologie, a description of the process. It differs very 

 little from that followed by the Chinese. A piece of nacre is sawn 

 from a shell of the required form, and placed between the mantle 

 and the shell of a nacle-producing mollusc ; when sufficiently coated, 

 it is filled with mastic, and a small plate of mother-of-pearl placed 

 at the back. In regard to British pearls, the author stated that the 

 first notice of the gem was by Tacitus, in his Life of Agricola; and 

 that the pearls were the product of the fresh- water mussel of our 

 rivers (Unio margaritafcra) was very evident from the description 

 that they were "not very orient, but pale and wan." To the 

 theory advanced by Arnoldi in 1690, anew by Sir Everard Home in 

 1818, and also by Kellart in 1858, that pearls, or rather their 

 nuclei, were due to the sterile ova of the molluscs which produced 

 them, the author gave his decided opposition, as, from all the facts 

 which he had observed, pearls were entirely due to a secretion from 

 the mantle of the animal. 



To illustrate the structure of pearls, Mr. Bryson exhibited a large 



