1899] PHYLOGENY OF THE RODENTS 389 



Phylogeny of the Rodents. 



The two preceding notes may be said to have dealt in great part with 

 little details about Eodents, and it is at once relevant and pleasant to 

 direct attention to a recent work which deals with Eodents as a whole. 

 We refer to Tycho Tullberg's great work, " Ueber das System der 

 Nagethiere. Eine phylogenetische Studie." (K. Gesellschaft der 

 Wissenschaften zu Upsala, 1899, pp. 514, 57 plates.) Beginning with 

 an introduction which discusses the canons of phylogenetic inquiry and 

 the general problem on hand, the author passes to a detailed statement 

 of his anatomical results. On the foundation furnished by these he 

 rears his phylogenetic system, proceeding in an orderly way which it is 

 a pleasure to follow, discussing adaptation after adaptation, and the 

 possible causes of various lines of structural change characteristic of 

 the sub-orders and families. The fourth part of the big book deals 

 with the distribution of Eodents in the past and present. He attaches 

 little importance to the alleged affinities between Eodents and Mar- 

 supials ; he emphasises the contrasts between Duplicidentata and 

 Simplicidentata, but does not think that these are inconsistent with the 

 view that both arose from a common pre-Eodent stock ; and finally he 

 suggests a genealogical tree of the order. To discuss his decisions on 

 affinities in brief compass would be impossible, but the work is 

 impressive as a phylogenetic study in which a vigorous attempt has 

 been made not only to trace the possible steps in the evolution of an 

 order, but to detect the possible causes which determined the direction 

 of these steps. 



Phylogeny of Rust. 



The origin of the rust fungi has recently given rise to a con- 

 siderable amount of discussion, and Professor Dietel, in an interest- 

 ing paper (Bot. Ccntralbl. lxxix. Nos. 3-4), considers the question of 

 their descent from one or more plurivorous forms — forms, that is, 

 which inhabited indifferently hosts belonging to the most widely 

 different families of flowering plants. At the present day, however, 

 only one species, a Crunartium, is known to retain this peculiarity, 

 having been shown by Fischer to be capable of life on plants belonging 

 to both Eanunculaceae and Asclepiadeae. But Professor Dietel 

 adduces a mass of collateral evidence which seems to show that the 

 balance of probability at least lies on the side of his hypothesis. It 

 would indeed be difficult to account on any other grounds for the close 

 morphological resemblances existing between forms which, while 

 biologically distinct and inhabiting plants belonging to the most widely 

 different families, are at the same time almost indistinguishable by any 



