1869.] and Membranipora Bengalemis. 53 



and I may mention, that one of my specimens moved in 24 hours by 

 gradually contracting and expanding its base* four inches on a level 

 horizontal bottom, and three inches on the perpendicular side of the 

 glass, so as to reach the surface of the water; in all therefore seven 

 inches. All the specimens shewed a particular liking to move nearer 

 to the surface of the water. The above shews that the Sagartia has 

 the power to move progressively at about the rate of 0.26 of an inch in 

 one hour, which is comparatively a very quick motion for these usually 

 sessile animals. 



The species is also common all along the banks of the Mutlah river. 

 During low water the specimens often remain for hours exposed to the 

 direct influence of the sun, attached to wooden pillars, stems of trees, 

 &c. Each specimen always retains a large quantity of water during 

 the time of exposure, and gives a portion of it up when disturbed. 



In conclusion I have only to mention a few words regarding the 

 chemical constituents of the brackish water, in which the animals 

 were found living, as compared with those of sea water. Mr. D. 

 Waldie, who very kindly undertook to make an analysis of the 

 water, tells me that 1000 grs, contain a total quantity of solids of 

 12.87 grs., of which are 0.78 sulphuric acid (anhydrous), 0.78 

 magnesia and 0.23 lime. Mr. Waldie further observes, " the arrange- 

 ment of the constituents is arbitrary ; supposing the acids and bases 

 are combined in accordance with the analyses usually given of sea- 

 water, it will stand as follows : — 



Chloride of Sodium (including potassium), 9.81 



„ „ Calcium, » ... 0.46 



„ ,, Magnesium, 0.93 



Sulphate of Magnesia, , 1.17 



Carbonic acid, &c, 0.50 



12.87 



This will be found very nearly the composition of sea-water as to its 

 principal constituents, but in quantity amounting only to very nearly 

 one-third of sea-water for the same volume of water." Dana in his 

 Manuel of Mineralogy also states that the amount of solid substances 

 in sea-water changes between 32 and 37 parts in 1000 pts. of water. 

 * Measuring about one inch in diameter. 



