10 



Dr. E. P. Perman and G. A. S. Atkinson. 



suggesting that it is not capable of living a long time free from the 

 colony, and the character of the cytoplasm indicating that when the 

 ovum is set free it is very buoyant, and is probably fertilised and 

 passes through the early stages of its development suspended in the 

 water. 



It is almost certain that the medusa does not digest food and 

 nourish the ova after its escape from the ampulla, and I am inclined 

 to believe that after a few pulsations which are sufficient to carry it 

 away from the region of the colony, the ova are set free and the 

 medusa dies. 



Correction. — In a former communication to the Royal Society (4), I 

 described certain cells in the coenosarc of Millepore from Celebes as 

 ova. Since the discovery of the female medusa, I have carefully 

 re-examined my preparations, and satisfied myself that I made a 

 mistake. These cells are not ova, but the cells which ultimately give 

 rise to the large kind of nematocyst. 



LITERATUKE. 



1. Duerden, J. E. *' Zoophyte collecting in Bluefields Bay," 'Journal of the 



Institute of Jamaica,' March, 1899. 



2. Hickson, S. J. " The Medusae of Millepora Murrayi" ' Quart. Journ. Micros. 



Sci.,' 1891. 



3. " Notes on the Collection of Specimens of the genus Millepora, obtained 



by Mr. Stanley Gardiner at Funafuti," * Zool. Soc. Proc.,' 1898. 



4. " The Sexual Cells and Early Stages of Development of Millepora plicata,' 



' Phil. Trans.,' B, vol. 179. 



" Vapour-density of Bromine at High Temperatures;" By E. P. 

 Peeman, D.Sc, and G. A. S. Atkinson, B.Sc. Communicated 

 by Professor Kamsay, F.E.S. Eeceived November 14, — Eead 

 December 7, 1899. 



It has been proved by one of us in a previous paper"^ that the 

 vapour-density of bromine is normal up to a temperature of 279° C, a 

 result in entire opposition to the numbers obtained by J. J. Thomson.! 



We have now determined the densities at temperatures ranging 

 from about 600° C. to 1050° C. by a modification of the former method, 

 the chief difference being that the globe was not filled with the vapour 

 by boiling out the excess of liquid, as in the usual method, but by 

 admitting the bromine, already in the form of vapour, to the globe 

 frhich remained in the furnace throughout the experiment. 



Apjoaratiifi used. — A is a porcelain globe (fig. 1), in some experiments 



* ' Eoy. Soc. Proc.,' vol. 48, p. 45. 

 t ' Roy. Soc. Proc.,' vol. 42, p. 345. 



