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T H E 



AQUARIUM 



a rich one for investigators, but one that 

 is of general interest to fish breeders as 

 well. The plant and animal life of which 

 plankton is formed, furnishes the first 

 food of the newly-hatched fish and more 

 mature individuals of many species. It 

 is this phase of the subject that will 

 prove of interest to the aquarist who 

 may not have the facilities or the in- 

 clination to study the purely scientific 

 aspect of the problem. The economic 

 and the scientific viewpoints are, how- 

 ever, closely related. 



The diatom is one of the many con- 

 stituents of plankton, and has received 

 a good deal of attention from micro- 

 scopists in recent years. No greater 

 proof of its importance as a food for fish 

 can be deduced than the fact that the 

 scientist in quest of specimens loses no 

 opportunity if examining the stomachs 

 of mollusks and fish, for there it is that 

 he is sure to find a goodly collection. 

 Many a rare specimen has been added 

 to the cabinet of the student by this 

 means. 



The diatoms are a large group of 

 plants, so very small that the aid of the 

 microscope is necessary to reveal their 

 diversity of beautiful forms. They thrive 

 in both fresh and salt water; so abund- 

 ant and widely distributed arc they that 

 there is scarcely a pond or ditch in which 

 specimens may not be found. That they 

 have existed in vast numbers for a?ons 

 of time their silicious remains, which 

 are found in all parts of the world, fre- 

 quently in almost pure fossil deposits 

 which are of the utmost commercial 

 value, give testimony. Many dental and 

 metal polishes, the action of which is 

 abrasive, not chemical, contain as cut- 

 ting material the remains of the diatom. 

 In boring artesian wells these fossils 

 have been brought up from a depth of 



()00 feet, a fact indicative of their great 

 age and long life period on the earth. 

 As to the vast extent of such deposits it 

 is a fact worthy of notice, that the city 

 of Richmond, Virginia, is built upon a 

 strata of almost pure diatom remains, 

 in some places lying fifty feet below the 

 surface. The process of forming such de- 

 ])osits is going on at the present time in 

 the bottoms of our rivers and lakes. 



Formerly, naturalists placed this fami- 

 ly in the animal kingdom in consequence 

 of their peculiar movements; at the 

 present time, however, a more intimate 

 acquaintance with their nature and hab- 

 its, acquired by the aid of improved 

 microscopes and confirmed by chemical 

 experiments, has resulted in their being 

 transferred to the vegetable kingdom. 



The plant consists of a siHcious en- 

 velope of three parts, made up some- 

 what after the fashion of the old card- 

 board pill-box, with top and bottom 

 joined by a ring. They are of every 

 conceivable shape, all microscopic in 

 size. Their great beauty consists in the 

 marking or sculpture of the envelope, 

 which is greatly diversified in its minute 

 pattern, some si:)ecies being marked with 

 parallel lines so fine, that 9(),{)()0 of them 

 measure but one inch in breadth. 



The frustulcs contain protoplasm; 

 whether or not it is structural is a ques- 

 tion that has been widely debated, as 

 has also the peculiar power of move- 

 ment. Diatoms are able to jjroceed back- 

 ward or forward, with no visible means 

 of propulsion, and after much discus- 

 sion the ciuestion remains a mooted one. 



I have been informed that a method 

 has been evolved to propagate diatoms 

 as a commercial food for oysters, but no 

 details on the subject are at present 

 available. If successful, the discovery 

 will prove a great boon to fish breeders. 



