12 



DIATOMACEiE. 



[Al.GAl.S. 



Order I. DIATOMACEjE. Brittleworts. 



,,■,„_.,._ A„,,rdli Suit \ii. (1824) ; KUtzino, in Linncea, 8.529; Part of Chaodiues anS Fra- 

 DW S Bm T&B& «"«. 3. and 4. (18231 ; Endlich. Gen. I.; Ral/s. in Ann. Nat. Hut. 



Diagnosis. — Crystalline, angular, fragmentary bodies, brittle, and multiplying bij 



spontaneous separation. 

 Crystalline fragmentary bodies, generally bounded by right lines, rarely included in 

 curved lines, Bat, stiff, brittle, usually nestling in slime, uniting into various forms, and 



then separating again. 



Those who have ever examined the surface of stones constantly moistened by water, 

 the glass of hothouses, the face of rocks in thesea,or of walls where the sun never shines, 

 or the hard paths in damp parts of gardens after rain, cannot fail to have remarked a 

 green mucous slime with which such places are covered. This slime consists of Algals 

 Tn their simplest state of organisation ; they have been called Chaodinese by Bory de 

 St. Vincent, whose account of them is to the following effect: " Theshme resembles a 

 layer of albumen spread with a brush; it exfoliates in drying, and finally becomes 

 risible by the manner in which it colours green or deep brown. One might call it a 

 provisional creation waiting to be organised, and then assuming different forms, accord- 

 ing to the nature of the corpuscles which penetrate it or develop among it. It may 

 further be said to be the origin of two very distinct existences, the one certainly animal, 

 the other purely vegetable. This matter lying among amorphous mucus consists, in 

 its simplest state, of solitary, spherical corpuscles ; these corpuscles are afterwards 

 luped, agglomerated, or chained together, so producing more complex states of 

 organisation. Sometimes the mucus, which acts as the basis or matrix of the corpuscles, 

 when it is found in water, which is the most favourable medium for its development, 

 lengthens, thickens, and finally forms masses of some inches extent, which float and 

 fix themselves to aquatic plants. These masses are at first like the spawn offish, but 

 they sunn change colour, and become green, inconsequence of the formation of interior 

 stable corpuscles. Often, however, they assume a milky or ferruginous appearance ; 



and if in this state they are examined 



under a microscope, they will be found 



completely filled with the animalcules 



called Navicularise,Lunuluise, and Sty- 



larise, assembled in such dense crowds 



as to be incapable of swimming. In 



this state the animalcules are inert. 



Are they developed here, or have they 



found then' way to such a nidus, and have they 



hindered the development of the green corpuscles ? 



Is the mucus in which they he the same to them 



as the albuminous substance in which the eggs of 



many aquatic animals are deposited ? At present 



\\r have no means of answering these questions." 



These form, no doubt, the extreme limits of the 

 Vegetable and Animal Kingdom. Their regular 

 form, and the power of separating into distinct 

 particles, which the most of them have, are almost 

 as much the attributes of the mineral, as of the 

 vegetable, or even animal kingdom. Agardh in- 

 cludes them among plants. Kiitzing asserts that 

 their life is as much animal as vegetable ; and that, 

 at all events, Aehnanthcs, Gomphonema, Exilaria, Fragila- 

 ria, Meloseira, Schizonema, Micromega, and Berkleya, are 

 at least plants, if Frustulia, Cymbella, Navicula, Surirella, 

 &c, arc animalcules. He has also recently ascertained, that 

 the frustules of Micromega are metamorphosed into green 

 globular spores. Dr. Dickie of Aberdeen has observed some- 

 thing of the same kind. Mr. Ralls, who has paid great attention to the history of these 



Pig.IL 



I , II.— 1. Blddulphia ;2. Qrammonema : 8. Eunotia ; 4. Achnanthes ; 5. Amphitetras ; 6. Gloionema, 

 1'iction once referred to this order, but determined by Mr. Berkeley to be the eggs of au insect. 



