754 



THE POPULAR SCIENCE MONTHLY. 



ture presented in any other light, unless it 

 were given as a bare descriptive catalogue 

 of details. 



With each group (considered as a special 

 study) are given a brief sketch of the struct- 

 ure and habits of some of its leading forms, 

 their affinities, embryology, and a very use- 

 ful table of the literature of the subject. 

 A list of the authors referred to indicates 

 clearly how few Americans have contributed 

 to a knowledge of the subject. 



The advanced character of the work is 

 seen in the adoption of Haeckel's terms for 

 different conditions of the embryo, such as 

 the morula stage, planula stage, gastrula 

 stage, etc. The ascidian stage is also recog- 

 nized in the development of Vertebrata. 

 Amphiozus is considered separately from the 

 fishes, the BracJdopoda are placed among 

 the worms. Altogether it forms one of the 

 most valuable works of science yet pub- 

 lis'hed in this country, and it is safe to say 

 that no working naturalist can do without it. 



As a second edition of the work must 

 soon be demanded, we trust it may be ac- 

 companied by a table of contents. 



AbstPvACT of Results of a Study of the 

 Genera Geomts and Thomomys, with 

 Addenda on the Osteology of Geomy- 

 iDM. By Dr. Elliot Coues. Washing- 

 ton : Government Printing-Office, 1875. 

 Pp. 74. 



This is a reprint from Major J. W. 

 Powell's report of his explorations of the 

 Colorado River, giving a full scientific ac- 

 count of the little animals known on the 

 Western prairies as Pocket Gophers. Re- 

 garding the two genera Geomys and Thomo- 

 mys as constituting a perfectly natural group 

 of the grade of a family, Geomyidce, the au- 

 thor describes them as " among the heaviest 

 for their inches of any animals in this coun- 

 try, of squat, bunchy shape, with short, thick 

 limbs, a short tail, very small or rudimen- 

 tary ears, small eyes, no appreciable neck, 

 and thick, blunt head ; and they are as 

 completely subterranean as the mole itself. 

 They are rarely or momentarily seen above 

 the ground ; they excavate endless galleries 

 in the earth in their search for food, fre- 

 quently coming to the surface to throw out 

 the earth in heaps, but plugging up these 

 orifices as soon as they have served their 

 purpose." 



Geomys contains five (some authors say 

 seven) well-defined species ; Thomomys but 

 a single species, including three recogniz- 

 able races, out of which, by the process of 

 species-mongering so common with earlier 

 naturalists, a dozen separate species were 

 made. While in Geomys the links have disap- 

 peared and the species are well-pronounced, 

 in Thomomys the separation is incomplete, 

 and the connecting forms still visible. " The 

 genus appears to be working into a number 

 of species, but the process is still far from 

 completion." Adopting modern philosophi- 

 cal views, the author's tendency is to re- 

 duce the number of species, seeing only 

 races or varieties where others claim to 

 have found well-defined species. The sev- 

 eral species constituting the family are sepa- 

 rately described. The cranial and dental 

 characters of the group are afterward treat- 

 ed, and the work closes with a further de- 

 scription, communicated by Prof. G. Brown 

 Goode, of Geomys tuza, a form confined to 

 Florida, Alabama, and Georgia, and there 

 known as Salamanders. 



Prof. Coues has the rare faculty of 

 making even technical descriptions interest- 

 ing, and for this reason the work commends 

 itself to the attention of other than scien- 

 tific readers. 



Practical Hints on the Selection and Use 

 OF THE Microscope. By John Phin. 

 New York : The Industrial Publication 

 Co., 1875. Pp. 131. Price, 75 cts. 



In the preface to this little book the au- 

 thor tells us that it is intended for begin- 

 ners in the use of the microscope, a pur- 

 pose that appears to have been kept well in 

 mind in the subsequent pages, as the ex- 

 planations are clear, the directions explicit 

 and suitably detailed ; and nothing has 

 been attempted that lies beyond the un- 

 derstanding of any intelligent girl or boy 

 of fifteen. After pointing out the numerous 

 applications of the instrument, that are 

 every day extending, the simple and com- 

 pound microscope, and the essential parts 

 of each, are described. The various forms 

 in use are next enumerated, with brief de- 

 scriptions of the most noted ; and then fol- 

 low practical direction* for the selection of 

 a microscope, and the requisite accessory 

 apparatus. Illumination, the manipulation 

 and care of the instrument, and the collec- 



