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PHYSICAL GEOGRAPHY. 



best, at the outset, to devote a few pages to a sketch of their nat- 

 ural history, presenting familiar and readily understood descriptions of 

 their forms illustrated by figures, their habits, modes of growth and 

 reproduction, and manner of occurrence in nature, so that the value of 

 a knowledge of them may be comprehended, and the reader be able, if 

 he desire so to do, to follow up their study and learn where they are to 

 be found, and how they may be collected, prepared, and examined. 



It is a remarkable fact that these beautiful and wonderful atomies, the 

 diatomacex, arc so little known to biologists in general, who, we find, 

 have neglected in a remarkable manner to make themselves acquainted 

 with the so-called lower forms of life, confining to a great extent their 

 investigations to a study of the larger groups. This doubtless has arisen 

 mainly from the fact that they cannot generally be seen and much less 

 studied by the unassisted eye, but require, for the full elucidation of their 

 anatomy and physiology, the most perfect appliances of modern skill, as 

 epitomized in the achromatic compound microscope. Now, however, 

 that the microscope is coming into more general use among scientific 

 observers, it is to be hoped that some obscure points relating to this 

 group of organisms, more particularly connected with their mode of 

 reproduction, as well as the subjects of evolution, abiogenesis, and classi- 

 fication, which, it is considered, may be more thoroughly studied in 

 these apparently simple forms than in the more complexly organized 

 forms of existence, will be elucidated, or, at all events, have considerable 

 light thrown upon them. Unfortunately, perhaps, the forms of the di- 

 atomaccac are so beautiful and attractive, that, as they have been in the 

 manner mentioned neglected by accomplished biologists, they have been 

 collected, observed, figured, and described by totally incompetent per- 

 sons, who, in very few cases, have possessed the training which would 

 qualify them for undertaking the investigation of organisms of which so 

 little is known, and whose position in the plan of being even is not 

 thoroughly established. Hence, a great deal of that which has been pub- 

 lished on this subject is totally useless, if it be not in many cases 

 absolutely harmful, tending to confuse rather than simplify matters, 

 and render the little that is known concerning their life-history obscure. 

 The natural consequence has been that students of the diatomaccne 

 have fallen somewhat into disrepute, and, in some cases, observers have 



