WATER. 



[ 685 ] 



WHALEBONE. 



green Confervoid Algae is by no means a 

 sure sign of impurity (properly so called) in 

 water; for some will only grow in very 

 clear and pure water, while many of them 

 may be regarded as agents of purification. 

 The presence of Zygnemacese, however, and 

 Diatomaceae is particularly objectionable, as 

 they become very fcetid in decomposition, 

 which generally takes place very soon when 

 they are disturbed and injured. When large 

 quantities of the minute Algae appear in 

 water, discolouring it over extensive surfaces, 

 the microscope will enable us to detect the 

 nature of the object producing the appear- 

 ance, but will scarcely be requisite to prove 

 the impurity of the water. 



Coloration of Water. — Under this head 

 we shall refer to those plants and animals 

 which most commonly produce such appear- 

 ances, premising that the commonest cases 

 of coloration depend upon suspended mineral 

 substances (mud), of different colours accord- 

 ing to the soils washed by the water. 



1. Producing a general green colom', or a 

 thick film on the surface. — Protococcus 

 [Chlamidojnonas, ^hi\, Diselmis, Duj.), very 

 common in the spring; and various Nosto- 

 chaceous Algae, as Trichormus, Conio- 

 PHYTON, &c. (see NosTOCHACE^; many 

 with a bluish tinge); Polycystis, Kiitz., 

 forming a granular verdigris-green layer; 

 various Palmellace^e ; Euglena viridis, 

 &c. [The Desmidiace^ form greenish 

 patches at the bottom of water or on plants, 

 as do certain Oscillatoriace^.] 



2. Producing a red colour in fresh water. 

 — Astasia hcemafodes, Ehr., species of 

 Daphnia. Some Naidina produce a red 

 colour on the mud in shallow water. Red 

 forms of species of Protococcus (see also 

 Red Snow). — In salt water, Diselmis 

 Dunalii, Du}. ; Trichodesmium. 



3. A brown cloudy appearance often ap- 

 pears in masses near the source of small 

 springs of water flowing out of blue clay, or 

 in pools on peat-bogs. This mostly consists 

 of peroxide of iron ; but sometimes a similar 

 brown appearance is produced in pools by 

 collections of amorphous granular decaying 

 organic matter, in which occur great abun- 

 dance of certain Oscillatori^, Diato- 

 MACE^, Infusoria, and Rotatoria. 

 The obscure mycelioid structure called by 

 Kiitzing Leptothrix ochracea produces a 

 yellowish-brown tint. Diatomaceae often 

 form a yellowish-brown coat on mud at the 

 bottom of water. Many Rotatoria and larger 

 Infusoria (Paramecia, &e.), when abun- 



dant, give water a shghtly milky appear- 

 ance. 



The above list is undoubtedly very imper- 

 fect, but may afford some useful hints. 

 Microscopists who meet with such colora- 

 tions will naturally examine them carefully ; 

 they will find further information under the 

 heads of the articles cited. 



WATER-BEARS. See Tardigrada. 



WEISSIA, Hedwig.— A genus of Pottia- 

 ceous Mosses, variously defined by different 

 authors, related to Gymnostomum. W. con- 

 troversa, Hedw. {W. viridula, C. Miill.) is 

 common. Wilson includes Blindia here, 

 and separates Rhabdoweissia {W.fugax and 

 denticulata). 



WELLS, DARK. See Introduction, 

 p. xvi. 



WHALEBONE.— In whales the teeth 

 are rudimentary ; and arising from a depres- 

 sion in the upper jaw on each side are a 

 number of parallel horny plates, many feet 

 in length, which project downwards; these 

 plates, which are technically known as fins 

 or blades, constitute whalebone, and through 

 them the water containing the animals upon 

 which the whale lives is strained, and the 

 food thus obtained. These plates are situ- 

 ated upon a vascular membrane, folds of 

 which enter a cavity at their base, which is 

 the portion connected with the jaw. 



Whalebone may be pretty easily divided 

 into longitudinal laminae and fibres ; but 

 these are only secondary forms resulting 

 from the aggregation of a number of cells, 

 of which whalebone wholly consists. 



On examining a transverse section of a 

 blade or plate of whalebone with the naked 

 eye, or a lens, two structures are readily 

 distinguishable ; an inner porous -looking 

 medullary portion, surrounded by an outer 

 compact or cortical substance. A longitu- 

 dinal section through the plate exhibits a 

 number of dark lines or stripes, from about 

 1-100 to 1-150" in diameter, parallel to 

 each other and to the axis of the plate, and 

 corresponding to the pores seen in the trans- 

 verse section. These strijies, which have 

 been called whalebone canals, but which we 

 shall denominate medullary lines, are seen 

 to be surrounded by a paler substance. 



With a higher power (^ inch), the trans- 

 verse section exhibits in the centre a number 

 of rounded apertm-es or circles corresponding 

 to the pores (PI. 1/. fig. 31), surrounded by 

 very fine, concentric, interrupted dark lines; 

 whilst towards the circumference these lines 

 run parallel to the surface of the plate. In 



