5 6o SCIENCE PROGRESS 



marked off from the lower mammals by the fact that they alone possess a 

 placenta. This is not the case. The author himself admits that in one of the 

 Didelphia, Perameles, a placenta is present. Now, if this is so, that alone should 

 be sufficient for him to remove Perameles from the Marsupialia, an obviously 

 impossible proceeding. It would appear as if he has accepted on trust a state- 

 ment made long ago by some one who was not acquainted with the early develop- 

 mental phenomena in marsupials, and the fact is that there is no reason to regard 

 Perameles as exceptional. Many, perhaps the majority, of the marsupials have 

 placentae. It so happens that this criticism does not alter the classification given, 

 which rests on surer anatomical grounds, but it is quite time that this oft-quoted 

 statement was given up. 



The book, as a whole, is exceptionally good, and the illustrations worthy of 

 special note. A copious index and a well-drawn-up glossary allow of ready 

 reference, and enable a reader not versed in palasontological terminology to 

 follow intelligibly the remarkable animal histories that are so well related in its 

 pages. In it are presented a very clear idea of the most important animal 

 migrations, both from without and within the continent itself, that have taken 

 place, and also of the changes that have occurred in the structure of the 

 mammals as the regions once more or less wooded became transformed into open, 

 grassy plains. 



It is one of the most interesting, as well as most useful, books on palaeontology 

 that have appeared. 



C. H. O'D. 



Entomology, with special reference to its Biological and Economic Aspects. By 

 Justus Watson Folsom, Sc.D. (Harvard). Second revised edition, with 4 

 plates and 304 text-figures. [Pp. vi + 402.] (Philadelphia : P. Blakiston's 

 Son &Co., 1913.) 

 This second edition of Dr. Folsom's interesting work will doubtless receive a 

 warm welcome from entomological students as well as from the general reader, to 

 whom it is also intended to appeal. Much new matter has been incorporated, 

 notably an entire chapter on the important subject of transmission of diseases by 

 insects ; a few new text-figures have also been introduced and the bibliography 

 has been considerably extended. The opening chapter, relating to general 

 classification, is purposely brief, owing to the existence of many excellent works on 

 this subject. The system adopted, however, is essentially that of Brauer with 

 certain modifications by Packard. The Anatomy and Physiology of insects are 

 then dealt with in an effective and interesting manner, being succeeded by an 

 account of their Development, both embryonic and post-embryonic. The three 

 following chapters (IV, V, & VI) are concerned with the Adaptations of Aquatic 

 Insects, Colour and Coloration, and Adaptive Coloration. Chapters VII, VIII, and 

 IX are of a more economic nature, and are entitled respectively Insects in Relation 

 to Plants, Insects in Relation to other Animals — in which prominence is given to 

 their connection with birds — and Transmission of Diseases by Insects. The last- 

 named subject, sparingly dealt with in the first edition, covers 19 pages and is 

 divided into sections relating to the diseases under consideration. The subject 

 matter, however, although one of the chief additions to the revised volume, is 

 unfortunately hardly up to date ; for instance, under the section Trypanosomiases, 

 no mention is made of the transmission, by Glossina morsitans, of the Rhodesian 

 form of sleeping sickness, although this was shown to be the case as early as 

 March 191 2. The genus Glossina, also, is stated to contain only eight species, 



