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have the name attached to the specimen upon the first opportunity, 

 and not left merely to memory, and it then becomes a useful 

 assistant in other determinations. (3) Every specimen which it is 

 desirable to keep should be carefully laid past and arranged with 

 others in the most convenient way for reference. 

 I shall indicate briefly — 



(1) Where the Ostracoda are principally to be found. 



(2) What season of the year is most favourable for procuring 

 them. 



(3) By what means they may best be secured. 



(4) How to preserve them most conveniently for inspection and 

 reference. 



I. Places where to be found. — They are to be found in lakes, 

 tarns, ponds, lagoons, canals, ditches, and often in very small 

 patches of water, and in slow-running streams ; but in the latter 

 by no means commonly, except in weedy recesses protected from 

 the currents, or where clumps of thickly-growing plants abound. 



Nowhere, throughout Scotland, is there any want of such places 

 either in number or variety, whether we regard the depth of water, 

 varying from the thinnest covering to the deepest lakes, or their 

 situations, ranging from the sea level to high mountain tarns ; or 

 the character of the basin in which they lie, rock, peat, clay, &c; 

 or, lastly, the impregnated mineral contents. Ostracoda are 

 generally more abundant in the smaller tarns or ponds, overgrown 

 with weeds, than in deep and large sheets of water, where the 

 surging of the waves is unfavourable to marginal vegetation ; yet 

 I often find, that places greatly overgrown with plants are not 

 always the richest in Ostracoda, but sometimes the reverse — probably 

 in such cases by affording more suitable conditions to a greater 

 host of enemies. Ostracoda are occasionally obtained in small tarns 

 and ponds where the water has been nearly dried up, leaving only 

 a little at some central depression ; and even in the damp mud, 

 whence the water has disappeared, good gatherings are met with, 

 as well as in the scanty water of furrows in old pasture land, and 

 which are dry during the greater part of the summer. It is indeed 

 surprising, as regards many of these patches of water, how speedily 

 after rain they are found swarming with Ostracoda and other 

 Microzoa. In some instances it has been observed that, after the 

 rains certain species are absent which had been present before the 



