OP THE diatohe-t:. 77 



from time to time rises to the sm-face of the water and carries up with it 

 some of the deposit in the form of a scum, Avhich gets blown to leeward, and 

 may be readily collected from the edge of the pond quite free from particles 

 of mud and other impurities. 



" Good and rare specimens have been obtained from the stomachs of Ho- 

 lothuridae and other Mollusca which inhabit deep water, and are often thrown 

 on shore after severe gales of v^dnd. These animals may be merely dried and 

 preserved just as found, and the contents of the stomach obtained afterwards 

 by dissection. Shells and stones, covered with seaweed, &c., from deep water, 

 also afford most interesting and little-known forms. The rougher these are, 

 the better (they ought by no means to be cleaned). Deep-sea soundings 

 (especially those from great depths) should be presei-ved ; for they are often 

 exclusively DiatomaceoiLS. 



" Yerv rare species have often been fonned in immense quantities in the 

 arctic and antarctic regions by melting the ' pancake ice,' rendered brownish 

 by these microscopic shells. The sea is also often observed discoloiu^ed with 

 brownish patches, which should be collected, and the water filtered through 

 blotting-paper or cotton wool : the residuum will frequently turn out to be 

 composed of Diatomeae. It is also highly interesting to collect and examine 

 the impalpable dust which occasionally falls into the folds of the sails of ships 

 at sea." 



Scallops and other MolliLSca often contain rich and rare collections in their 

 stomachs. In Ascidia (e. g. Phallusia sulcata^ Ascidia mentula) Mr. ISTorman 

 and the Rev. E. CressweU found an abundant source. Mr. J^orman adds, in 

 a further note kindly sent us — " The Ascidians, whose stomachs are almost 

 always so loaded with Diatomaceous frustules, are to be found abundantly 

 on the shells of oysters dredged in deep water, and readily procurable from 

 the trawlers. 



" The Salpce (found so abundantly floating on the surface of the sea in warm 

 latitudes) aflbrd very pure gatherings. The roots of the various species of 

 mangrove, growing in the dense swamps of rivers and estuaries in the tropical 

 regions of Africa, Australia, and the Eastern Archipelago, are said to be fre- 

 quently covered with a brownish mucous shme very rich in Diatomese. I 

 liave also obtained very pure gatherings from the roots of the Dutch rushes, 

 as imported, and from the Zostera marina from the Baltic, used for stuffing 

 beds, &c., by upholsterers. Stones, moreover, brought as ballast from abroad, 

 will amply pay the diligent collector by yielding foreign and perhaps rare 

 species. The roots of aquatic plants from tropical countries, stored in her- 

 baria, would, if properly examined, peld many interesting forms of Diatoms." 



Indeed we may add, generally, that the roots of land plants, particularly 

 of mosses, hchens, &c., growing around trees on the ground, or upon them, 

 are fniitful in Diatomese, and, in fact, of some of the rarer fonns. In the 

 ■N^umber of the Microscoincal Transactions just published (July 1858, p. 79), 

 Col. Baddeley notes the occurrence of Diatoms in considerable numbers in 

 the Koctiluca miliaris. They are the chief constituents of a mass of dark 

 matter near the nucleus, and lie in the so-called vacuoles, into which they 

 enter from the mouth. This occurrence suggests an easy method of obtaining 

 different marine species of Diatomese in their natural state, often alive, and 

 with their endochrome perfect. The Colonel discovered in this way several 

 rarer species, and gives a list of nearly 50 which he identified, besides not a 

 few forms of whose true name he was uncertain. To extract the Diatoma- 

 ceous mass from the interior of the Noctilucce, Col. Baddeley recommends 

 that the seawater and its h\'ing freight be poured, on arriving home, in a 

 white hand-basin, and be let stand for an hour or two. " This rough treat- 



