498 NEW AND RARE FRESHWATER ALGiE, 



316, 317, 327, 337, 340a, 345, 347, 352. The pool is the drain, 

 age of a considerable area of ground swampy after rain, and is 

 about 2 feet deep in the centre; in droughty weather, it is often 

 entirely dry."*^ 



On account of its unpromising appearance, and to secure ever}^- 

 thing that might be present, a quantity of water was taken from 

 a spot where there was a growth of coarse weeds, the weeds being 

 well shaken up, and the bottom disturbed also to some extent. 

 This water was strained through a plankton-net of common calico, 

 ground-samples from the swamp being sometimes added. Several 

 gallons would be treated in this way, and the last quart, or so, 

 of water and sediment taken home in a tin and decanted. 



During the periods mentioned above, a gathering was taken, 

 on an average, once a month, the main portion of the water being 

 drawn from the same spot. The results show the importance of 

 a regular periodic examination of a pond. The desmids and 

 diatoms were fairly constant, but the Myxo2:>hyceai, Volvocacece, 

 and Protococcoidece presented, from month to month, an ap- 

 parently endless succession of forms, new, uncommon, or not 

 previously recorded. Rarely could any of these be noted in two 

 successive gatherings, and very often they were never seen again. 

 For instance, of Chlamydomonas, 10 different forms, new or rare, 

 were noted; of Carteria, 5; of Phacotus, 2; of Volvox, 2; of 

 Oocystis, 7; of Tetraedy^on, 7; of Geminella, 4. Yet, in two 

 summers, the most that could be said was, that a few of them 

 had been recorded a second time. 



Of course the swamp, with its ever-changing conditions of life, 

 is the real breeding-ground of all these forms, the pool being 

 only the repository of them, Chlamydomonas and Gay-teria are 

 notoriously dependent on rainfall, and are very sensitive to stag- 

 nation; but I find that forms of Oocystis and Tetraedron are 

 just as irregular in their appearance. Probably, the reason is 



* Swampy pools of this sort are the best places to search for new and 

 rare forms of microscopic life; permanent waters, on the other hand, can 

 generally be relied on to jaeld a micro-flora and fauna of unvarying 

 character. 



