616 



SCIENCE 



[N. S. Vol. XXXIX. No. 1008 



tyla — horses, titanotheres, rhinoceroses; the 

 Artiodaetyla — swine, camels, deer ; the Probos- 

 cidea; and of the primitive ungulates, the 

 Amblypoda and Condylarthra. There follow 

 a number of chapters devoted to the peculiar 

 South American ungulates, on which Professor 

 Scott is so pronounced an authority, and 

 these give place to a discussion of the carni- 

 vores, primates, edentates and marsupials. 



Chapter XVIII. is philosophical, in that it 

 expresses very clearly Doctor Scott's ideas 

 concerning the modes of mammalian evolu- 

 tion. He states in explanation of the varia- 

 tions found between the " family trees " that 

 " It is quite impracticable to construct a gene- 

 tic series without making certain assumptions 

 as to the manner in which the developmental 

 processes operated and the kinds of modifi- 

 cation that actually did occur," and the facts 

 upon which these assumptions are based are 

 ascertained by several distinct methods. Of 

 these the oldest is comparative anatomy, an 

 accurate knowledge of which is indispensable 

 to the use of the others. The second is that 

 of embryology, for, while Haeckel's famous 

 biogenetic law, wherein the life history of the 

 individual is supposed to give a resume of 

 that of the race, is proved not to be implicitly 

 trustworthy for the interpretation of struc- 

 tural features, nevertheless the information 

 attained through study of the embryonic stages 

 is of the greatest service in the solution of 

 zoological problems. 



The third method, experimental zoology, 

 especially that part known as genetics, has 

 also taught us much; but the fourth, paleon- 

 tology, despite the imperfection of the record 

 due to the irretrievable loss of much of the 

 past history of life, nevertheless has the pre- 

 eminent advantage of offering to the student 

 the actual stages of development, as it pre- 

 serves the original documents and in the true 

 order of succession. 



In summation. Professor Scott remarks : 

 " It is only too clear that the principles as 

 to the modes of mammalian development 

 which can be deduced from the history of the 

 various groups must, for the most part, be 

 stated in a cautious and tentative manner, so 



as not to give an undue appearance of cer- 

 tainty to preliminary conclusions, which 

 should be held as subject to revision with the 

 advance of knowledge. Much has, however, 

 been already learned, and there is every rea- 

 son to hope that experimental zoology and 

 paleontology, by combining their resources, 

 will eventually shed full light upon a subject 

 of such exceptional difficulty" (p. 663). A 

 full glossary completes the volume. 



The illustrations are in part from photo- 

 graphs of living mammals and clear anatom- 

 ical drawings of certain essential skeletal 

 features, but what will interest the general 

 reader most are the admirably drawn recon- 

 structions of extinct forms done by E. Bruce 

 Horsfall under the careful supervision of Pro- 

 fessor Scott. There are also others by 

 Charles R. Knight, whose work always has a 

 realism which no other artist of the pre- 

 historic has ever attained. 



In the production of this work Professor 

 Scott has done a lasting service to the serious 

 student of paleontology, as well as to the lay 

 reader, and it is to be hoped that the admir- 

 ably conceived and executed volume will have 

 the appreciation it deserves. 



EiCHARD S. Lull 



Yale Univebsitt 



The Hill Folk. Eeport on a Eural Commu- 

 nity of Hereditary Defectives. By Florence 

 H. Danielson, M.A., and Charles B. Daven- 

 port. Eugenics Eecord Office. Memoir 

 No. 1. 



As explained in the preface, this is the first 

 of a projected series which is intended to em- 

 body some of the more extended research of the 

 Eecord Office. Dr. Davenport calls attention 

 to the fact of its primary value to sociologists 

 rather than to students of inheritance traits — 

 which latter will require much more extended 

 study, which, we are assured, will come later. 

 This Hill Folk study began with pedigrees 

 of some of the inmates of the Monson State 

 Hospital at Palmer, Mass., and extended to a 

 town of 2,000 inhabitants in a fertile valley 

 on a railroad between prosperous cities. The 

 town is frequented by tourists who about 



