192 Hunting for Diatoms. 



Some of the oyster shells from deep water are worth ex- 

 amining for marine Algae, or, what is even better, the greenish, 

 leathery-looking ascidians attached to them. The ascidians are 

 regular feeders on diatoms, and their stomach contents often 

 yield a rich harvest of deep-water forms difficult to obtain in 

 any other way. Perhaps we may be securing the rare Biddul- 

 pJiia regina, at any rate, Bidd. Baileyii and aurita. We will 

 take some for future examination, for the curious Rhizosolenia 

 styliformis is almost sure to be there. 



Let us step into a boat and examine that ship's bottom and 

 sides, which look so brown with a growth of conferva and bar- 

 nacles. Here the spoon becomes of use. Scrape very gently 

 where the deposit is the darkest in colour, and let us see what 

 we have got—Achnanthes longipes and brevipes in abundance. 

 These are common enough elsewhere in the timber ponds, so 

 we will only secure the little thing in zig-zag filaments, for this 

 is probably Diatoma hyalinum, or, perhaps, the rare Hyalosira 

 delicatula. 



Is it not singular that such delicate filaments, hanging to- 

 gether by the angles of the frustules, should be able to with- 

 stand the rushing of the vessel through the water during the 

 long voyage she has just completed ? 



The ballast heap must not be passed without examining. 

 Here are stones densely covered with marine Algae and Coral- 

 lines, which we will scrape off, and store away for after ex- 

 amination. Biddulphia pulcliella, Amphitetras, Grammatophora 

 serpentina, or possibly some of the beautiful foreign species of 

 Aulacodiscus, may reward our trouble, for this ballast is brought 

 from all parts of the world. The only matter of regret is the 

 difficulty in ascertaining the exact localities. 



Let us now take some of the Zostera which is being landed 

 on the quay in large bales ; it is extensively imported from the 

 Baltic as Alva marina, for stuffing chairs and mattresses. 

 Cocconeis scutellum and diaphana, with Epithemia and a medley 

 of other forms, are generally found parasitic on the Zostera, 

 and may be easily separated by maceration in weak acid. 



But what are those brown bundles landing from the steamer ? 

 These are " Dutch rushes/' for coopers' purposes and chair- 

 bottoms, and are well worth examining, for, growing as they 

 do in brackish water in Holland, the sheath at the base is often 

 completely coated with diatoms, Coscinodiscus svhtih's, for in- 

 stance, with other good things, such as Eitpodiscus argus and 

 Triceratium favus. 



Nor must we pass these cargoes of bones discharging into 

 lighters. See, some of the larger bones have evidently been 

 lying in the water some time, for they are covered with a green 

 incrustation. Let us scrape away the incrustation, for we may 



