80. ia 
musical sound is 16 per second. The vibrations of the Fly’s wing | : 
gave two degrees of vibration: a, 225 double vibrations per sec. ie 
and b, 150 per sec. 
XXII.— Our Sponges—sx J. T. Hitxrrer, M.R.C.8.Eng. 
DECEMBER 2, 1886. 
This paper referred mainly to the advance lately Bea, 
common with all branches of Natural History, in the knowledge o: 
. the structure and function of sponges ; so that there was no difficult 
in recognizing them as animals. A general description was given 
of the structure of their component parts, together with their — 
classification, and ample illustrations were made by well selected — 
specimens and microscopic slides of all points alluded to. ‘The — 
paper was a preliminary one to another that is to follow, settin; 
forth the author’s more local and original knowledge. : 
2 ted 
[recoded . . > Sa 
~s ¥ 
Bre : 
“Pt o 
= ) ‘She 
“> ine 
ae i 
