36 diatom a ri:i:. 



its relations to particular forms, bat the silicified cachet of 

 TriceraHum and of Coscinodiscus is as palpable in the pillared 

 rock or the California stratum as in the recent condition, or in 

 the softer "deposits" of Nottingham, Md., and of Moron, 

 Spain, or in the Guano accumulations of the Chincha and other 

 islands. 



"Preparation of the DiatomaceaV' ought strictly to signify 

 the preservation of individuals or groups of these organisms in 

 a permanent way, and their arrangement in a condition suitable 

 for study and future reference. We would begin with the deep 

 sea soundings and end with animated pool-water. It is not our 

 purpose, however, to discuss at present the various devices 

 adopted to accomplish a task so extended; but we desire to 

 point out those methods of isolating the siliceous parts of Dia- 

 toms to which experience has given reputation. 



It may be worth while to premise by stating — what is, of 

 course, familiar to the student — that the coveted forms are to 

 be met with in a great variety of conditions, either swarming 

 fresh and full of life in pools, ponds, or estuaries, clothed in 

 fibres of green, brown, or yellow, or clustering together in 

 springs, pullulating in lakes and rivers, or tossed by the waves 

 of the great ocean itself. In some of these situations the 

 Diatomacea} become and are the pabulum of myriads of beings, 

 in whose bodies, as the Acalephs, the* Salpidce, the Molluscs, and 

 the Holothuridce, their siliceous remains are constantly found by 

 the microscopists, who use these and other creatures for their 

 dredgers. They live with and upon other AUja j , and are met 

 with in the green ooze of Confervoids, and even among the 

 Muscldo?,. 



As ancient or recently fossilized, however, forming strata of 

 considerable thickness, of widely different consistency and 

 density, and not unfrequently of wide-spread geographical dis- 

 tribution, the Diatomaceaj astonish even the workers in science 

 by the extent of their proliferation, and by the uneventful 

 quiet of their living and dying, apparently undisturbed for 

 whole ages in the conditions of their existence. Examples of 

 these tedious and slowly cumulative formations may be in- 

 stanced in Cassel, in California, in Jutland, and in Maryland 

 and Virginia, the latter furnishing so many varieties of con- 



