EDITORIAL GLEANINGS.
At the meeting of the Zoological Society, on the 4th inst., Dr. H. Lyster Jameson, M.A., read a paper "On the Origin of Pearls." The author's observations referred especially to Mytilus edulis, the Common Mussel. The pearls were found to be due to the presence of parasitic Distomid larvæ, which entered the subcutaneous tissues of the Mussel, and became surrounded with an epidermal sack similar in its characters to the outer shell-secreting epithelium of the mantle. If the Distoma died in the sack it became calcified, and formed the nucleus of a pearl, the pearl arising, like the shell itself, from the calcification of the cuticle of the epithelial cells. The parasite sometimes migrated out of the sack, in which case the nucleus of the pearl was inconspicuous. Dr. Jameson had investigated the life-history of this parasite, and found that it arose as a tail-less Cercarian larva, in sporocysts, in Tapes decussatus and Cardium edule. He had succeeded in infecting Mussels from Tapes in an aquarium. The adult stage of this parasite was apparently Distoma somatinæ, Levinsen, which occurs in the intestine of the Eider-Duck, and which the author had found in the Scoter or Black Duck (Œdemia nigra). The complicated life-history of the parasite, and the absence of organs of locomotion in the Cercaria-stage, sufficed to account for the anomalous and hitherto inexplicable distribution of pearl-bearing Mussels. Dr. Jameson had found that pearls were caused by similar parasites in several other species of Mollusca, including some of the Pearl-Oysters; and he believed that the artificial infection of the Pearl-Oysters could be effected in a similar manner to that which he had found successful in the case of the Common Mussel. When this was achieved the problem of artificially producing pearls would be solved.
Slowly but steadily the great collection of British Birds by Mr. F. Coburn, the well-known taxidermist, of Birmingham, is being built up. More than ten years have elapsed since the work was first entrusted to him by Mr. Baylis, of Birmingham, and it may be fifteen or even twenty years before the great task is completed. The statement suggests dilettante efforts, but, as a matter of fact, hard constant
