Febeuaey 25, 1898.] 



SCIENCE. 



283 



Inspection of the volume enables one to form 

 some idea of the relative activity in chemistry 

 at different periods; in 1792 there were three 

 papers published on the subjects included ; in 

 1840 there were 14 papers ; in 1860, 22 papers, 

 and in 1892 there were no less than 68 papers. 

 These numbers do not include abstracts and 

 reproductions of original publications. 



It is also interesting to note the relative fre- 

 quency of the occurrence of the names of cer- 

 tain chemists; thus J. W. Dobereiner published 

 43 papers between the years 1814 and 1845 ; 

 his great contemporary Berzelius, 25 papers 

 between 1812 and 1847; H. St. Clair Deville, a 

 generation later, published 31 papers (1852- 

 1882), and S. M. Jorgensen has published 27 

 papers between 1867 and 1896, his activity 

 being still productive. Of course, the number 

 of the papers does not indicate the relative 

 importance of the discoveries ; W. H. Wollas- 

 ton, for example, published only nine papers, 

 but his influence on the chemistry of platinum 

 has been notable. 



The volume is clearly printed and seems to 

 be quite free from typographical errors; Ed- 

 monde Fremy's name, however, appears as 

 Premy throughout the work, but Fremy never 

 used the accent on the first vowel in his name. 



Howe's ' Bibliography of Platinum ' will be 

 a necessity to every working chemist and to 

 every scientific library. 



H. Caerington Bolton. 



The Development of the Frog's Egg. An Intro- 

 duction to Experimental Embryology. By 

 Thomas Hunt Morgan, Ph.D., Professor of 

 Biology, Bryn Mawr College. New York 

 and London, The Macmillan Company. Pp. 

 xi + 192. Price, $1.60. 



As the first attempt to present a connected 

 account of the development of any animal from 

 the standpoint of the new experimental school 

 of morphologists. Professor Morgan's book on 

 the development of the frog will be received 

 with much interest. The time is ripe for a 

 summary of the experimental work on the early 

 stages of development, showing what has and 

 what has not been accomplished by this much 

 discussed method of investigation. Professor 

 Morgan gives us an account of the embryology 



of the frog, laying especial weight ' on the re- 

 sults of experimental work, in the belief that 

 the evidence from this source is the most in- 

 structive for an interpretation of the develop- 

 ment.' We shall hope, therefore, in its perusal 

 to learn how much has been accomplished in 

 making clear the course of events in the embry- 

 ology of a single animal by means of experi- 

 ment. The egg of the frog has become the 

 classical object for this sort of research, so that 

 a more favorable choice of subject for this pur- 

 pose could not be made. 



The scope of the work is not confined, how- 

 ever, to results achieved by experiment. The 

 book undertakes to give a ' continuous account 

 of the development, as far as that is possible, 

 from the time when the egg is forming to the 

 moment when the young tadpole issues from 

 the jelly membranes,' drawing upon both de- 

 scriptive accounts of the normal development 

 and experimental work to make it complete. 

 The sub-title, however, makes us justly expect 

 that the experimental results will form the 

 chief aim of the book. 



After a half-page introduction on the egg lay- 

 ing and copulation of the frog, Professor Morgan 

 opens his account in Chapter I. with a discus- 

 sion of the formation of the sex- cells, followed 

 in Chapter II. by a description of the processes 

 of egg laying, formation of the polar bodies and 

 fertilization. With Chapter III. we enter upon 

 the first account of experimental work, a short 

 resume of the researches of Pfliiger, Born and 

 others upon cross- fertilization in the Amphibia. 



Chapter IV. treats of the normal cleavage of 

 the frog's egg, with the variations met with 

 under natural conditions. The question is 

 proposed : What determines the plane of cleav- 

 age in the unsegmented egg ? Roux's conten- 

 tion that this is determined by the plane of ap- 

 position of the two pronuclei is stated, but the 

 actual determining factor is held to be still in 

 doubt, with the evidence rather against Eoux's 

 view. Further discussion of this question is 

 reserved for a later chapter. As to the factors 

 determining the form and arrangement of the 

 cleaving cells, the author discusses here only 

 the surface tension theory, again reserving, 

 according to a plan which can hardly be said 

 to conduce to unity other supposed factors 



