Zoological Society. 303 



mechanical force, as is the case when vegetable parasites make their 

 way through the cell-membranes of Conferva or other plants. 

 Besides this, it deserves also to be remembered that nearly all the 

 parasites here spoken of occur in marine animals. 



In concluding this notice, I may further mention that these 

 parasites afford an excellent means for demonstrating the double- 

 refracting power of the shells of the several genera mentioned in 

 this communication. I was first struck with this fact in examining 

 a horizontal section of Lima scabra obtained from Dr. Carpenter, 

 and finding that many tubuli appeared double. In following this 

 matter, it was easy to show that all the tubuli running in a certain 

 direction, and in an oblique way through the section, appeared 

 simple at the upper surface of it, and became double in the inferior 

 layers, so that the distance of the two images increased with the 

 shortening of the focus. When the preparation was inverted, the 

 reverse was the case. The same phenomena as in Lima were also 

 observed in Anomia, Ostrea, Murex truncatus, Turbo rugosus, 

 Tritonium cretaceum, and Balanus, the shells of which animals have 

 therefore all such a structure that they refract the light in the same 

 way as the well-known double-refracting crystals*. 



ZOOLOGICAL SOCIETY. 



January 11, 1859.— Dr. Gray, F.R.S., V.P., in the Chair. 



Notes on the "Mooruk" (Casuarius Bennettii). 

 By George Bennett. 



On the 26th of October 1858, the 'Oberon' cutter of forty-eight 

 tons arrived in Sydney, having two fine young specimens of the 

 "Mooruk" on board, stated to be male and female. On going on 

 board I found them confined in a very small space ; and the Captain 

 informed me he had had them eight months, that he procured 

 them soon after his arrival at New Britain for Sydney, and since 

 that time had been trading about the islands, having these birds on 

 board ; they were fed principally upon yams. I observed they were 

 in poor condition, but healthy in appearance, and plumage in good 

 order. They were about half the size of the specimen sent to En- 

 gland ; but one, apparently the male bird, appeared a little larger 

 than the other. Captain Devlin informs me that the natives capture 

 them very young, soon after they are hatched, and rear them by 

 hand. The natives rarely or never can capture the adult bird, as 

 they are so very shy and difficult of approach — the native weapons 

 being ineffectual against so rapid and wary a bird. These birds are 

 very swift of foot, and possess great strength in the legs ; on the 



* According to Brewster (Bibl. Univ. de Geneve, 1836, ii. 182), who seems the 

 only person who has hitherto observed the double- refracting power of a shell, 

 viz. of the mother-of-pearl, that shell (Meleagrina) shows the same phenomena 

 as the double-axed double-refracting Arragonite, — on which question I am not as 

 yet able to give an opinion. 



