THE VICTORIAN NATURALIST. 107 



Ascidians, but I was only once successful with any of these latter 

 methods, and this was with stomachs of some fish of the flounder 

 family. 



I have not, so far, said anything as to fossil deposits. These, 

 as you know, are very numerous in different parts of the world, 

 and in some cases very rich in forms not now existing in the 

 living state. I propose only to allude to the more important 

 deposits which have so far been noted in Victoria. Those most 

 worthy of attention are the brackish water deposits of South 

 Yarra and West Melbourne, the latter being very extensive and 

 containing many fine species. Freshwater deposits have been 

 found at Amherst, Talbot, and Lancefield, and several other 

 deposits of minor importance are recorded from Gippsland. 

 What appears most remarkable to me is that, so far as I know, 

 and certainly as far as I have myself sought, no trace of diatoms 

 exists in any of our tertiary deposits at Mornington, Bairnsdale, 

 or Muddy Creek. Nor have I seen any trace of silicious sponge 

 spicules; it would thus appear that, if ever present, they had been 

 dissolved by the chemical action of water, or otherwise destroyed. 

 So much for collection. 



Now as to the cleaning of diatoms. — It would be impossible 

 within the limits of this paper to give anything like a detailed 

 description of the many processes for accomplishing this end. 

 The mere enumeration of the chemicals and apparatus regarded 

 by some operators as needful would weary you. I therefore 

 propose to take two typical examples, one recent and one fossil, 

 and describe my own method of dealing with them. I may say 

 at the outset that scarcely any two gatherings, either recent or 

 fossil, require precisely the same treatment ; slight modifications 

 are necessary in nearly every case, in accordance with the nature 

 of the material to be dealt with. As to apparatus and acids, the 

 following are necessary : — Two strainers (preferably of silk), one 

 sufficiently coarse to pass the largest diatoms, the other as fine as 

 possible, so as to retain the smallest ; several conical glass jugs of 

 about a quart capacity, one or two small beaker glasses, a glass 

 syringe, and circular glass dish ; a lamp or other source of heat 

 must be at hand, together with a plentiful supply of clean water. 

 We shall require two acids only, sulphuric and nitric, both of 

 ordinary commercial strength ; and a small quantity of chlorate of 

 potash and some crystals of common washing soda complete the 

 list of what is absolutely essential. We will treat, first of all, a 

 recent gathering of diatoms in mud, such as might be obtained 

 from Hobson's Bay, and regard this as fairly representative of 

 any recent gathering. Our material, consisting, say, of about half 

 a pint of liquid mud containing a fair sprinkling of diatoms — 

 of the presence of which we are assured from previous examina- 



