OF THE DIATOME^. 87 



some inhospitable and barren districts of Europe — for instance, in some 

 localities of Lapland and of Himgaiy, and in other parts of the world. 

 Ehrenberg mentions a sort of earth under the name of " Tanah/' eaten in 

 Samarang and Java, which overlays some moimtains of Java at several places 

 at a height of 4000 feet. It is generally solid, plastic, and sticky; it is 

 rolled and diied in the shape of small sticks over a charcoal fire, and is eaten 

 as a delicacy. An examination of this earth disclosed 3 or 4 species of 

 Polygastrica and 13 of PhytoKtharia. 



It has been attempted to make the specific characters of Diatomaceous de- 

 posits of critical value in deciding on the date and superposition of rocks. 

 However, the geographical distribution of these beings is as yet insufficiently 

 knoTVTi ; and eveiy day reveals the fact that species deemed peculiai* to some 

 one locality are to be foimd in others, and to have at least a very wide range. 

 We have already quoted some examples of apparent limited diffusion in our 

 remarks on geographical distribution ; it is therefore not necessary to illustrate 

 the subject fui^ther in this place. 



The circumstance that some one or two species seem at times peculiar to a 

 neighboui'hood, has encoiu'aged antiquarians to seize on it with the hope of 

 determining the locahty whence the clay was procui^ed from which ancient 

 specimens of pottery or porcelain were manufactured. 



Another practical pm^pose to which the shells of Diatomece have been put 

 is as test-objects for microscopes, the penetrating and defining powers of which 

 are measured by their abihty to detect and demonstrate the existence and 

 natiu"e of certain markings on the siu'facc of the silicious epiderm — such, 

 for example, as the stria3 of PUurosigma. 



Ox TUE NATUEE OF DiATOMEiE, AYHETHEK AnIMALS OE PlAISTS VAEIOUS 



HYPOTHESES. — The natiu-e of the Diatomese is still a much-vexed question, 

 although the opinion of those natui^alists who hold them to be plants — mem- 

 bers of the great family of Algte — preponderates. Ehrenberg assumed their 

 animal natiu^e, and persuaded himself of the existence of a complicated organi- 

 zation, such as neither the researches of others can confii*m nor analogy sup- 

 port. In his latest papers on Organization, he has insisted most strongly on 

 the -apparent successful feeding of these organisms \vith particles of coloiu' 

 which entered A\ithin their interior. These experiments are not satisfactory, 

 and have failed in the hands of others ; it is besides quite clear, that the 

 umbilicus, at which he represented the coloiu'-granides to enter, is no real 

 opening in the lorica, but a tliickening of its epiderm. 



Prof. Meneghiui, now many years ago, penned a learned treatise to prove 

 the animality of the Diatomese ; but although he offered many ingenious argu- 

 ments to support his opinion, he did not succeed in establisliing it. Many de- 

 tails of structiu'e and organization and micro-chemical characters, ui^gedby him 

 in favour of their animal nature, have been considerably modified or entirely 

 set aside by subsequent researches ; and the general argument, that the varia- 

 tion fi'om recognized plants is in many particulars very marked, has only a 

 comparative or relative force, according to the extent of differential stmcture 

 of animals which may, on the other hypothesis, be set forth and proved. 



The distinguished Itahan naturalist indeed limits his design in the treatise 

 before us (On the Animal nature of the Diatomeoe, R. S. 1853) to disputing 

 Kiitzing's arguments for their vegetable nature, saying (p. 365), " Whilst 

 unable to confirm or refute the opinions of Ehrenberg, we seem to have 

 observed facts sufficient to disprove those of Kiitzing." 



On this same side are ranged Eocke, Eckhardt (a pupil of Ehrenberg), and 

 Prof. Bailey, who express thou- inabihty to reconcile some of the structural 

 details and physiological phenomena with vegetable organization. Schlcidcn 



