1886-87.] The Diatoms of Linlithgozv Loch. 81 



point, more particularly of the Ostracoda, from dredgings fur- 

 nished by the son of the late Prof Sir Wyville Thomson, 

 when fourteen species of crustaceans alone were found, be- 

 sides several other minute forms. It is well known, however, 

 that " pond life " is very capricious, some species being found 

 at one time in great abundance, while at another these may 

 be almost entirely absent, and their place filled by others, and 

 this altogether irrespective of the season of the year. It was 

 therefore determined to take some samples from the loch, and 

 a few bottles were filled from a boat in shallow water, — taking 

 care to include not only some of the mud or ooze, but also sub- 

 merged j)lants which had rusty - brown parasitic growths on 

 them, as these growths were in all probability diatomaceous in 

 character. When examined afterwards under the microscope, 

 many beautiful specimens of Eotifera and Vorticellee were ob- 

 served, besides entomostraca, amcebre, and numerous diatoms. 

 Unfortunately, after a few days most of these interesting organ- 

 isms began to disappear, probably for want of proper nourish- 

 ment, or because of the small quantity of water in which they 

 had been gathered; and by-and-by little or nothing was left 

 but the indestructible siliceous frustules of the diatoms which 

 had been seen shortly before under the microscope in the living 

 state, moving through the water. It was therefore determined 

 to secure these frustules, so as to preserve them in a permanent 

 form ; and Messrs Pearcey and Ptattray kindly lent their valu- 

 able aid in preparing and naming the specimens. The result 

 is, that to-night no fewer than twenty-three named forms are 

 shown under the microscope, while there are several others 

 which have not yet been identified. The full list is appended, 

 showing that Gomphonema is represented by five species and 

 varieties ; Navicula by four ; Cymbella, Diatoma, Fragilaria, 

 and Synedra by two each ; while other forms of fresh-water 

 diatoms are also present, including the beautiful star-shaped 

 Asterionella formosa. These diatoms are all, of course, very 

 minute, requiring a high power of the microscope in order to 

 examine them — fresh-water forms, as a rule, being smaller than 

 those found in salt water. Additional species and varieties of 

 diatoms are doubtless present in the loch, and those members 

 who turn their attention to this subject are recommended to 

 make farther investigations, as opportunity offers. 



VOL. II. F 



