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 Rodents, and it is at once relevant and pleasant to 
direct attention to a recent work which deals with Rodents 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 Rodents in the past and present. He attaches 
little importance to the alleged affinities between Rodents 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-Rodent 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. Centralbl. \xxix. 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 Cronartium, is known to retain this peculiarity, 
having been shown by Fischer to be capable of life on plants belonging 
to both Ranunculaceae 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 
