144 ON THE COLLECTION AND 



Algae Cocconeis, Acnanthes, Striafella, Tabellaria^ Grammatophora^ 

 Ist/wiia, PodosphcEiiia^ and RJiipidophora. In salt marshes we 

 shall obtain Amphipleura and Melosira^ whilst in shady situa- 

 tions Cai7ipylodiscus and Coschwdisais abound. The sides of 

 ditches in marshes are often covered with various species of 

 Surirella, Navicida^ Fleurosigma, Auiphiprora, and Amphoi'a. 



Some i^\yi Diatomacese are peculiarly autumnal, as Hcemocladia 

 Martiana^ Berkleya fragilis, Dickeia piimata^ and Striatella uni- 

 pundata. 



In clear running fresh-water ditches, the plants and stones often 

 have long streams of yellowish-brown slimy matter adhering to 

 them, generally composed almost entirely of filamentous species, as 

 Schizonema and Mtcro??tega. 



The layers of Diatomaceous fronds on the surface of mud, are, 

 according to Pritchard, often covered with bead-like bubbles of 

 oxygen, which from time to time rise to the surface of the water, 

 and carry up with them some of the deposit in the form of a 

 scum, and which may be readily skimmed off the surface of the 

 pond with an ordinary iron spoon, nearly, if not quite, free from 

 mud and other impurities. 



Good and rare specimens may be obtained from the stomachs 

 of Holothuridians, Ascidians, and Molluscs, which inhabit deep 

 water, and are often thrown ashore after a gale. All that is 

 required is to dry them thoroughly, and afterwards submit the 

 contents of the stomach to dissection. 



To those collectors who are resident inland, I would suggest 

 that the liquid in the tinned oysters sold by Messrs. Lazenby and 

 Son, should be allowed to settle, and the deposit cleaned. The 

 results will give some beautiful spheres of Coscinodiscus and 

 other equally interesting forms. 



The washing of oyster shells also furnish us with Rhabdonema^ 

 Melosira, E7idictya^ and many well-known marine forms. The fact 

 of the Diatomacese rendering themselves apparent to the unaided 

 vision by their great accumulation, and the discolouration of the 

 water they inhabit is illustrated by Melosira ochracece, which occurs 

 in most chalybeate waters ; also by Goinphonenia gemijtattwi, 

 which forms a brown deposit on rocks in summer ; the same may 

 be said of Syiiedra ulna Schizonema in swift-running streams. 



