392 NATURAL SCIENCE. December, 



them about and catching them when in motion, or chase living 

 objects like the tail of their mother. (4) Games of combat — the 

 innumerable instances of these which are known seem to him to imply- 

 chiefly a preparation for future combats between males for the posses- 

 sion of females. He believes that the instinct to challenge and to 

 murder among all kinds of creatures is almost entirely confined to 

 males. And so in the further divisions of (5) games of love, including 

 the quest of bright colours and the practice of songs and cries, of (6) 

 architectural games, and (7, 8, and 9) games involving respectively 

 duties, imitation, and curiosity, the Professor carries out his general 

 thesis of the gradual replacement of instinct by experience. 



The psychologist will find a great deal of Professor Groos' book 

 worthy of study. Its theory of attention and the gradual evolution of 

 attention from curiosity is novel and interesting. From the point of 

 view of the biologist, the most interesting part is the attempt to place 

 a new meaning upon the period of youth, and to bring the activities 

 of youth under the influence of natural selection. 



Geographical Distribution. 



A Geographical History of Mammals. By R. Lydekker. (Cambridge Geo- 

 graphical Series.) Pp. xii. and 400. Cambridge : University Press, 1896 

 Price los. 6d. 



That of all the great sub-divisions of the animal kingdom, the 

 mammals supply the most important evidence in questions relating to 

 the former distribution of land and water, was long ago recognised by 

 Wallace. Their limited means of dispersal, the great abundance of 

 their fossil remains, and the consequent relatively complete knowledge 

 of their past history are the chief factors which give them this special 

 importance. It is true that of Pretertiary Mammalia little is known, 

 and therefore other groups must be employed in attempting to 

 determine the distribution of land and water in the earlier geological 

 periods ; but in later times, from the Lowest Eocene upwards and in 

 many quarters of the globe, numerous mammalian faunas have been 

 discovered which supply the strongest available basis for such specu- 

 lations. This being the case, a volume on the distribution of this 

 group, written by one who is equally familiar with living and extinct 

 forms, will be peculiarly welcome both to zoologists and geologists. 

 Such a book had indeed become a necessity, so great have been the 

 advances in our knowledge of the MammaUa, particularly of the 

 extinct forms, during the last few years, whole faunas having been 

 discovered and described, which throw floods of light on many disputed 

 questions, and render necessary a revision of many previously accepted 

 opinions. The present volume supplies just what was wanted, being 

 thoroughly up-to-date, and clearly and impartially written. 



The sub-divisions of the land areas of the globe adopted by the 

 author are very similar to those suggested by Blanford in 1890. 

 Three great " realms," the Notogeic, Neogeic, and Arctogeic, form 

 the main divisions ; of these, the first includes the AustraHan, 

 Polynesian, Hawaiian, and Austro-Malayan " regions " ; the second, 

 the Neo-tropical region only ; the third, the Malagasy, Ethiopian, 

 Oriental, Holarctic, and Sonoran regions. The advantage of this 

 scheme is that it throws into strong relief the extreme distinctness of 

 the Australasian and South American faunas ; on the other hand, the 

 " regions " are of very unequal value. Perhaps the most interesting 

 and important parts of the book are the chapters on the Notogeic and 

 Neogeic realms. The origin of the Marsupials of Notogaea is dis- 



