ON COLLECTING OBJECTS. 97 



matter of a shade somewhat different to any hitherto observed, ad- 

 hering to some of the parts of the trench, being partially submerged, 

 and having a somewhat tremulous motion on agitating the water. This 

 is a species of Schizonema ; and it consists of a quantity of gelatinous 

 hollow filaments filled with an immense number of bright-brown shuttle- 

 shaped bodies, like very minute naviculce. 



It is not necessary to be particular about collecting the specimen 

 free from mud, as the filaments are so tough that the mud can be 

 readily washed away by shaking the whole violently in a bottle of 

 water, and pouring off the mud, without at all injuring the specimen. 

 The Amphisporium alatv/m communicates a somewhat frothy appear- 

 ance to the otherwise clear water, and to get any quantity of this 

 requires a little management ; but by skimming the surface with the 

 spoon, and using one of the larger bottles, an abundance may readily be 

 obtained. Between, the sea-wall and the river the marsh is intersected 

 in every direction with a number of meandering creeks, being in some 

 places eight to ten feet deep, though in others quite shallow ; but it 

 is exceedingly difficult to make one's way amongst them, and I have 

 never found them so prolific any where, on the few occasions of my 

 visiting the place, as in the parts more away from the influence of 

 the tide. It will be observed, that the brilliant brown colour, of a 

 deep but bright cinnamon tint, is one of the best indications of the 

 presence of diatomacece; and though this is by no means universal, 

 the variation is most frequently dependent upon the presence of some- 

 thing which qualifies the tint. The peculiarity of the colour is due to 

 the endochrome contained in the frustule ; and this must in general be 

 got rid of before the beautiful and delicate marking can be made out. 

 But it is highly advantageous and instructive to view them in a living 

 state ; and this should be done as soon as possible after reaching home 

 with all specimens procured from salt-water localities, as they rapidly 

 putrefy in confinement, and emit a most disgusting odour, not unlike 

 that arising from a box of inferior congreve-matches. 



Washing in fresh water, and then immersing in creosote water, pre- 

 serves many of the species in a very natural-looking manner ; but they 

 are kiUed by the fresh water, and the endochrome becomes much con- 

 densed in the Pleurosig-mata and some other species. The addition of 

 spirits quite spoils the appearance of the frustules, as it dissolves the 

 endochrome. 



There is another salt-marsh a little farther down the same railway, 

 at Higham, which it would be well to explore. 



The most favourable months for procuring diatomaceae, are April, 



H 



