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POPULAR SCIENCE REVIEW. 
inch immersion lens, yielding a magnifying power of from 700 
to 2,000 diameters and upwards, may be obtained at Mr. Charles 
Baker’s, of 244 High Holborn, for the modest sum of 3l. Such 
an object-glass will be found equal to interpreting the form and 
structure of any of the numerous types figured in the accom- 
panying plates, and with such a lens, indeed, the whole of these 
forms were, with but few exceptions, in the first place discovered 
and delineated by the writer. 
The mechanical apparatus being decided on and obtained, it 
remains only to select the material for investigation. Either 
salt or fresh water will be found to yield its quota of the types 
required, and those frequenting the last-named element, being 
usually the more accessible, will most probably command first 
notice. Here the investigator will find his time most profitably 
employed in procuring from the nearest weedy pond or ditch a 
bottleful of the finely divided leaves of Myriophyllum, or of 
tangled confervoid growths, in either case selecting more espe- 
cially those brown-hued specimens coloured by a dense incrus- 
tation of other more minute vegetable and animal parasitic 
growths. Care should likewise be taken to enclose with the 
water as large a number as possible of the specimens of Cyclops 
and other Entomostraca abundant in such situations, and to 
which will be frequently found attached species rarely, if ever, 
to be met with elsewhere. Patiently exploring every filamen- 
tous division of the above-mentioned weeds with the lower of 
the two powers employed, it will be scarcely possible to miss 
encountering one or more of the species illustrated in the ac- 
companying plates. As first seen with this lower or reconnoitring 
power, it will of course be almost impossible to distinguish 
the characteristic collar, and the monads will appear as mere 
luminous specks adherent to the plants under examination. 
Meeting with these, the higher power must be brought into 
focus, when the true nature of the organisms will be revealed. 
Among the varieties which are likely at first to be encountered 
are, perhaps, the two loricated species Salpingoeca amphoridium 
and fusiformis (See Plate IV. figs. 3 and 23), the former often 
completely incrusting several consecutive joints of various 
thread-like confervae, while the latter will occur as solitary indi- 
viduals scattered about at uncertain intervals. On the stronger 
fulcrum for support afforded by the leaf-partitions of Myrio- 
phyllum, the illoricate species Codosigo, pulcherrima (Plate 
III. fig. 9) is often present in great profusion, its sociable pe- 
dicellate colonies being so thickly placed as to present the appear- 
ance of a perfect little forest of crystal-fruited trees. More 
rarely, under similar conditions, the extremely elegant and 
symmetrically tripartite branching pedicellate form Codosiga 
umbellata (Plate III. fig. 4) may be likewise met with. 
