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Show 140 DR. H. LYSTER JAMESON ON THE [Mar. 4, In one genus all the females are blue, thus proving that this beautiful green development is probably of a comparatively recent date. M. de Niceville tells us that when seen in sunlight these green specimens are gems of beauty, compared with which the most brilliant of the blue species are absolutely dull. Among many entomologists who have been most kind in lending me their insects, I must mention two in particular who have passed to the great majority. The late Dr. Staudinger sent m e over a considerable portion of his collection of this group, including all his types; whilst the late M . de Niceville (in whom India has lost a most energetic and untiring observer) was good enough to lend m e the whole of this portion of his collection; so that these two gentlemen alone furnished m e with well over two thousand specimens. M y warm thanks are due not only to these but to many others for much kind help. This Memoir will be printed entire in the Society's ' Transactions.' The following papers were read :- 1. On the Origin of Pearls. By H. LYSTER JAMESON, M.A., Ph.D. [Received February 7,1902.] (Plates XIV.-XVII.1 and Text-figures 22-24.) Most theories of Pearl-production have assumed that the " nucleus," whatever its origin may be, is the direct cause of the secretion of a true pearl, and that the latter arises as a result of the mollusc's endeavour to coat with carbonate of lime an irritating body. I do not propose in this paper to give yet another complete historical survey of the various hypotheses, dating back to the time of Pliny, which have been propounded. These theories have been summarized over and over again by writers on pearl-formation. The more recent ones may conveniently be grouped under the following heads:-That pearls are (1) concretions of shell-forming fluid (Reaumur, 1717); (2) shell-substance deposited around bodies or concretions of internal origin (Kiichenmeister, in part, 1856 ; von Hessling, 1858 ; Pagenstecher, 1858) ; (3) formed around an abortive or displaced ovum (Home, 1826 ; Kelaart, in part, 1857); (4) secreted to coat over a grain of sand ; (5) the result of injury to or perforation of the shell; (6) caused by a parasite (Filippi and others); (7) formed in an ampulla in the tissues (Hessling, 1858 ; Diguet, 1899). Several writers have allowed the possibility of two or more of these causes. The origin of the " grain-of-sand " theory is veiled in obscurity. 1 For explanation of the Plates, see p. 165. |
