40 



microscope will be of great service in examining them, and 

 will prove a never- ending source of interest and delight. 



" These minute forms are found in all waters, but the most 

 interesting species are those found in salt water, especially 

 shallow lagoons, salt-water marshes, estuaries of rivers, pools 

 left by the tide, &c. 



" Their presence in any quantity is always shewn by the 

 colour they impart to the aquatic plants and sea-weeds to 

 which they are found attached, and if found on the mud, which 

 is very frequently the case, they impart to it also a yellowish 

 brown colour approaching to black brown if in great numbers. 



" This brownish pellicle, if carefully removed with a spoon 

 (without disturbing the mud) will be found very pure. Capital 

 gatherings of Diatomacea3 might be obtained by carefully 

 scraping the brown-coloured layer from mooring posts, and 

 piles of wharfs and jetties. 



" In clear running ditches, the plants and stones have often 

 long streamers of yellowish brown slimy matter attached to 

 them, which is generally diatomaceous. 



" When found in large quantities on the mud, the layer is 

 often covered with bead-like bubbles of oxygen. This often 

 detaches them from the bottom and buoys them to the surface, 

 where they form a dense brown scum, which is blown to lee- 

 ward in large quantities, and presents the general appearance 

 of dark-coloured yeast. 



" In this form it may be collected in abundance, often quite 

 free from particles of sand and other impurities. 



" Good and rare species have been obtained from the sto- 

 machs of oysters, scallops and other shell-fish inhabiting 

 deep water. 



" The sea-cucumbers (HolothuridaJ found so frequently 

 in southern latitudes, ought to contain many species. 



" These animals might be simply dried and preserved just 

 as found, and the contents of the stomach afterwards obtained 

 by dissection. 



