800 Mr Connell on the Chemical Constitution of Gadolinite. 



Figs. 5. and 6. A very young comatula of the natural size, and 



magnified, a, a:, the vent, in front is the star-like mouth. 



bf bj Two of the dorsal cirri. 

 Fig. 7. Adult Comatula decacnemos. c, The dorsal cirri. 

 Fig. 8. Part of one of the arms seen in face, a, Ova protruding from 



the conceptacula. b, Ova just beginning to make their exit. 



c, One as yet filled with the ova. d, Ova magnified. 

 Figs. 9 and 10. Parasite of comatula magnified. 10. Turned over 



on its back ; m. Mouth ; f^ feet ; b, ova? 



On the Chemical Constitution of Gadolinite. By A. Connell, 

 Esq. F.R.S.E., &c. Communicated by the Author. 



According to the analysis of this mineral by Berzelius, its 

 constituents are yttria, protoxide of cerium, protoxide of iron, 

 and silica. It would appear, however, that Ekeberg had found 

 about 4 per cent, of glucina in a variety analyzed by him ; and 

 very lately an analysis has been published by Drs Thomson and 

 Steel, of a variety in which so large a proportion as 11.60 per cent, 

 of glucina appears.* The external characters of this latter 

 variety agree sufficiently with those usually assigned to gadolinite ; 

 but the proportion of oxide of cerium is considerably less than 

 in the analysis of Berzelius, as appears from the following com- 

 parison between one of Berzelius"* analysis and that of Dr 

 Thomson : — 



Farther, Dr Thomson's specimen was a large mass of the mineral, 

 weighing several ounces, and mixed with grains of platinum, 

 whilst, so far as I am aware, gadolinite had previously been only 

 observed crystallized, or disseminated in small grains or globules, 

 in other minerals. Its locality, also, was unknown. 



Although no doubt can be entertained that the mineral ana- 

 lyzed by Dr Thomson was a variety of gadolinite, yet the pecu- 

 liarities above alluded to appeared to me to make it a matter of 

 interest to examine again some specimen of the ordinary varieties 

 • Records of Science. June, 1835. 



