8 



KNOWLEDGE & SCIENTIFIC NEWS. 



[Feb., 1904. 



in these matters ; for instance, one foe, a Plectognathid 

 fish, which possibly devours very many oysters, at the 

 same time receives and passes on the parasite whicli 

 results in the production of pearls in others. 



The life-cycle of the pearl oyster is described from the 

 egg onwards to the adult animal, and the story unfolded 



excrescences on the interior of the shell were detected as 

 being due to the irritation caused by boring sponges and 

 burrowing worms, but the minute grains of sand or other 

 internal particles popularly supposed to form the nuclei 

 of pearls are considered only to do so under exceptional 

 circumstances. The majority of the best gems, on the 



Three transplanted Oysters showinjj rapid growth. I 



II. New'shell formed in 21 days. III. Oy 



is one of singular interest. Margaritifera vulgaris was, in 

 fact, most seriously studied ; partly in miniature experi- 

 mental tanks, with the first aid of the microscope ; again, 

 in the hauls of the tow-net ; and by means of diving 

 trials at the sea depths, where, it may be noted, the 

 oyster occurs on the rocky bottom in 5 to 10 fathoms of' 



The dotted line indicates the new shell formed— 23 days, 

 star showing a month's growth — Natural size. 



contrary, are caused by the stimulation of a parasitic worm 

 which becomes encased and dies. And this parasite is 

 the Cestode larval Tdrarhijnchits. Professor Herdman 

 purposes dealing with this aspect of the question of 

 pearl-formation at greater length later on. 



Finally, there is one general conclusion that is reached 

 in this opportune and admirable Report, and it is all-im- 

 portant. \Ve are told that there is no reason for any feeling 

 of despondency in regard to the future of the pearl fisheries 

 of Ceylon if they are treated scientifically. Adult oysters 

 are plentiful on some of the paars and seem for the most 

 part healthy and vigorous ; while young oysters in their 

 first year and masses of minute spat just deposited are 

 very abundant in many places. " The material exists, 

 ready for man's operations." 



[.According to a Times telegram from Colombo on December 

 gth, 190J, Captain Legge, Master .-Xttendant, on his return from 

 inspecting the pearl banks, has decided against the proposed 

 fishery this year. The next fishery will be in February, 1905.J 



Astronomical Notes* 



Valuation sample of Pearl Oysters in course of delivery from 

 the inspection boats. 



water. In the vicinity of the Manaar Gulf pearl banks 

 this element is so clear that under the rays of a high sun 

 the depths are brilliantly illuminated. A passing shadow 

 will cause the animals to immediately snap-to their 

 valves. 



As regards pearl -formation, some pearls or pearly 



Sir W. Ramsay on New Gases and Radium. 



Sir William Ramsay addressed the British .Astronomical 

 .Association on December 30, on the subject of " Stars and 

 Atoms." In the earlier part of his lecture he recounted the 

 history of the discovery of the new gases, .Argon, Helium. 

 Neon. Xenon, and Krj'pton, exhibiting representations of 

 their spectra, and explaining their places in the periodic 

 series. He dwelt specially on the last-named gas with refe- 

 rence to its connection with Aurorre, and showed that the 

 principal line in the auroral spectrum was the chief line 

 of Krypton. Passing then to the discovery of radium, he 

 described the properties of this element, including the three 

 kinds of rays that it gives off, and suggested that we might 

 find an analogy to the constitution of the molecule of this, the 

 densest of all known elements, if we imagined a closely aggre- 

 gated solar system, or better still, a stellar cluster, in which 

 the collisions were frequent, or at least the perturbations 

 often excessive, leading to the continual loss by the system of 

 members whose velocities thus attained a greater than the 

 critical. Such instability, he suggested, would be only per- 

 ceptible in the case of unusually dense elements. 



