54 



SCIENCE. 



SCIENCE: 



A Weekly Record of Scientific 

 Progress. 



JOHN MICHELS, Editor. 



Published at 



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P. O. Box 3838. 



SATURDAY, JULY 31, 1880. 



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 Broadway. 



PROFESSOR LEIDY'S " FRESH WATER RHIZO- 

 PODS OF NORTH AMERICA. " 



Dr. Leidy is acknowledged to be the highest 

 authority on the subject treated in his great work, 

 " Fresh Water Rhizopods of North America ; " a 

 criticism of the book becomes, therefore, a work of 

 supererogation, and we reserve to ourselves the 

 more pleasing task of pointing out its many beau- 

 ties and particularly its importance as one of the 

 most valuable contributions to the literature of 

 microscopic forms of life. 



Published by the Department of the Interior of 

 the United .States Government, and forming volume 

 twelve of the " Report of the United States Geo- 

 logical vSurvey of the Territories" in charge of 

 Professor V . V. Hayden, it is produced in a sump- 



tuous form which no private publisher would have 

 dared to imitate. 



Dr. Leidy's Report covers about three hundred 

 folio pages, illustrated by forty-eight full sized 

 plates, printed in colors in the highest style ot 

 lithography. 



It may be a superfluous question to most of our 

 readers, but as Dr. Leidy himself inquires in the first 

 page of his work, " What are Rhizods?" In re- 

 ply he says, " Rhizopoda are the simplest and 

 lowest forms of animal life, constituting the first 

 class of the Protozoa. They derive their name 

 from the Greek word rhiza, a root, and flous, a 

 foot. They are mostly microscopic beings, al- 

 though sometimes sufficiently large to appear as 

 conspicuous objects." We may add that the 

 essential characters are the gelatinous structureless 

 bodies, and the locomotive organs consisting of 

 variable retractile root like processes (pseudo-poda 

 or false feet). 



Their minuteness is compensated for by their 

 multitude and wide-world distribution ; essentially 

 aquatic they occur wherever there is moisture ; the 

 search for them may be commenced in the crevices 

 of the stones at your door step, and may be con- 

 tinued in every marsh, pool, ditch, pond, lake, sea 

 and ocean, and from the greatest depths of the latter 

 to the snow lines of mountains. 



The particular Rhizopods which form the subject 

 of the book now under consideration, are those 

 found in fresh water only, and Dr. Leidy expressly 

 states that his attention, during the four years en- 

 gaged, was directed more to the discovery and de- 

 termination of the various forms occurring in the 

 United States, than to the elaboration of details of 

 structure, habits, modes of development, and other 

 matters pertaining to their history. 



Although it is professedly an illustrated catalogue 

 of die fresh water Rhizopoda of North America, 

 we find most interesting and valuable contributions 

 to their life history which makes us regret that time 

 and opportunity did not permit Dr. Leidy to extend 

 his observations in this direction, for we know how 

 exhaustive such a treatise would have been from his 

 hands. 



Instead of writing a discursive essay upon Dr. 

 Leidy's book, already done by many brillant 

 writers, which, with a work so purely technical, 

 seems the least profitable method of treating the sub- 

 ject,we propose to take our readers through the book, 

 acting the part of a friendly guide, trusting by the 

 aid of twenty-two illustrations we have reproduced 

 for this purpose, not only to do justice to the work 

 in question, but to convey to those who have not 



