No. 413.} REVIEWS OF RECENT LITERATURE. 399 
his view may account for some of the variations, but even in these 
cases something more is needed to explain the concomitant changes. 
4. Variation of the costal elements at one end of a region is often 
associated with variation of an opposite nature of those at the other 
end. Several regions may be involved, and the two sides may vary 
independently. 
5. Variations, which separately seem either reversive or progres- 
sive, generally lose that appearance when the whole spine is 
considered. 
6. After the occurrence of the original error in development there 
is a tendency for the spine to assume as nearly as possible its nor- 
mal disposition and proportions. This, as do also concomitant vari- 
ations and indeed all development, implies a * vital principle." 
These deductions of the author naturally invite discussion ; but it 
will be of advantage if this be deferred until the material bearing on 
the points in question is still more abundant and the observations 
extended. Conclusions of this nature apply not only to the part 
under consideration but largely to the whole skeleton. 4A B. 
Notes.— Four * Cruciform Structures near Mitla" are described 
by Mr. M. H. Saville in Vol. XIII of the Bulletin of the American 
Museum of Natural History. After a scholarly summary of the 
history of previous explorations at Mitla the author confines his 
attention to the cruciform burial chambers which are unique in form 
and surpass all other tombs in Mexico or Central America in size 
and in beauty of stone work. 
“A Bilateral Division of the Parietal Bone in a Chimpanzee ; 
With a special Reference to the Oblique Sutures in the Parietal,” is 
the subject of a paper by Dr. Aleš Hrdlička, appearing in the same 
volume. It contains a detailed description of the skull of an adult 
male chimpanzee, with a discussion of the important problems con- 
nected with the abnormal parietal sutures. An oblique suture, the 
author believes, can be attributed to only three possible causes, as 
follows : an early fracture, a persistence of the original separation 
between the two centers from which the bone is developed, and a 
Coexistent difference between their relative positions ; the existence 
of à supernumerary third center of ossification. The brochure is 
illustrated by six outline drawings. 
In the Report of the Museums Association of the United Kingdom 
for 1898 Mr. Harlan I. Smith advises an “ ethnological arrangement 
