1887.] NATURAL SCIENCES OF PHILADELPHIA. 167 



pound microscope to bear upon a sponge growing under such cir- 

 cumstances ; a strong Coddington lens was tlie best that could be 

 applied to this work ; but a very fair share of su<icess was obtained 

 by the device of scattering small squares of mica among the grow- 

 ing gemmules, which, when covered by the young sponge, could be 

 removed to the stage of my instrument, covered with water in a 

 compressorium and examined comparatively at leisure. It was a 

 perpetual cause of astonishment to me, to see so large a production 

 of silicious spicules from a single gallon of water, in which the chem- 

 ist would probably have failed to find any such constituent. It is 

 worthy of consideration however, whether such silica as composed 

 the older spicules may not , at least when under the influence of the 

 growth force of the younger sponges, be to some extent soluble. 



Further observations regarding the late maturity and the winter 

 growth of some sponges will be found recorded in the general re- 

 marks concerning SponglUa aspinosa, S. lacustris etc. 



As to processes of gathering — I have already mentioned the ad- 

 vantages obtained by the use of the "scraper net" in relatively deep 

 water and in connection with perpendicular timbers etc. At depths 

 of two feet or less, great facility of action is gained by wearing high 

 rubber boots and wading after our specimens, to pick from the bot- 

 tom stones, sticks or pieces of waterlogged timber, under which they 

 may be concealed. Where the water is deeper, of course a boat 

 must be used, to approach the floating, submerged or dependent 

 sponge-bearing substances. A large, strong knife or a paper- 

 hanger's scraper will be found convenient for hand work at short 

 range. A case containing trays an inch or so in depth is suitable 

 for carrying the smaller specimens ; the larger will of course require 

 vessels of greater size. On reaching home or headquarters it is well 

 to select some specimens of characteristic shapes and containing 

 gemmules, for storage in dilute alcohol, making use of wide mouthed 

 bottles to avoid crushing them. The rest may be spread upon boards 

 in sheltered situations, in the shade (for the sun bleaches them rapidly) 

 and left to dry ; turning them every few hours to prevent decompo- 

 sition. If time is limited or the specimens are large, artificial heat 

 may be necessary ; but, whatever process is used, the drying must 

 be thorough, or mould will soon cover the sponges with a mycelium 

 which may be beautiful enough in itself, but is far from agreeable 

 or sightly as a feature of the sponge. Whether they are to be dried 

 or preserved in alcohol, they should be dealt with j^romptly and on 



