Hunting for Diatoms. 193 



find among it the fine Synedra crystallina or undulata, together 

 with valves of Goscinodiscus and Eupodiscus. Many good 

 gatherings have been procured from this source, especially 

 from cargoes coming from Constantinople, Smyrna, and the 

 Black Sea. 



Ask this sailor if he has any foreign shells still in the rough 

 state ; if he has any for sale, they are certainly worth securing 

 for the small Algas and Corallines found growing on them. 

 These, on being cleaned, often yield splendid results. Many of 

 the most beautiful and rare species of Gampylodiscus have been 

 obtained from this source. The Californian Haliotus shell is 

 almost certain to yield the fine Aulacodiscus Oregonus, Arachnoi- 

 discus, Hyalodiscus cervinus, and Biddulphia Boperi ; while the 

 Haliotus from New Zealand will probably furnish the rare 

 Aulacodiscus Beeverim and Macraeanus. 



The West Indian Strombus shells invariably yield beautiful 

 forms, such as Gampylodiscus-ecclesianus, ambiguus, and impe- 

 rialis. 



Vessels with guano are worth visiting. The Peruvian guano, 

 when properly prepared, yields the magnificent Asterolamprab 

 and Aulacodiscus scaber; while the Bolivian is even richer 

 in fine things, such as the superb Aulacodiscus formosus and 

 Comberi. Californian guano yields, among an infinite variety 

 of forms, many of great beauty and rarity, such as Aulacodiscus 

 margaritaceus and Biddulpliia Tuomeyii. Algoa Bay is fre- 

 quently rich in Aulacodiscus Petersii ; and, finally, the Ichaboe 

 guano, Eupodiscus Ehrenbergii, and other good things. 



The old mooring anchors and cables which are now lying 

 on the quay are covered with a marine incrustation, which on 

 examination will be found deserving of notice. 



We will now take a stroll towards the timber ponds, where 

 the timber often remains afloat for years. Here we see ample 

 traces of the objects of our search. The sides of the logs seem 

 quite covered with a tangled mass of the filamentous forms ; 

 but before we bottle up any of them, let us collect with the 

 spoon some of the brown pellicle which covers the surface of 

 the water. This proves to be a very pure gathering of Amphi- 

 prora constricta. Then let us collect some of the green TJlvcu 

 and Enter omorpha, growing on the sides of the timber, which 

 seems so brown and furry. With the Coddington lens we 

 find the brown tint is owing to a dense parasitic growth of 

 Achnantlies longipes and brevipes. The long brown filaments 

 are principally Melosira nummuloides and Borrerii, with Schizo- 

 nema crucigerum and Billwynii, mixed with Bacillaria paradoxa, 

 shooting into long filaments, then suddenly retreating until the 

 filament is closed again, one frustule sliding past the other in a 

 most marvellous manner. By the way, this species will live, 



