1890.] Zoology. 1203 
Further particulars on the above-reviewed ‘‘ preliminary," and of 
Herr Heymons’s other investigations in this line, will be looked for 
with considerable interest.—C, W. STILES, Leipzig, October, 1890. 
Studies on the Wrist and Ankle.—Dr. C. Emery! starts 
with Gegenbaur's morphological principle that the centrale must have 
had a primitively central position, and that where several centralia are 
present they form a connected group; but he rejects the views of 
Howes and Ridewood? that there may be a translocation of centralia 
to the radial and ulnar sides of the hand. He further accepts the 
views of Gótle and Leboucq regarding the rays of the carpal and tar- 
sal members. First he shows that in the hand of the larva of Rana 
esculenta traces of an intermedium are visible, and that the so-called 
centrale is a true centrale. Next he attacks the problem of the true 
nature of the so-called naviculare in the Anura. Comparing the car- 
pus and tarsus of a frog, the similarity of the navicularia in both is 
apparent, but the naviculare tarsi is apparently, as Wiedersheim has 
pointed out, the tarsale of the prehallux; hence, says Emery, the so- 
called thumb of the frog must be a prepollex, or otherwise the pre- 
hallux must be hallux, and then the last fibular toe would be post 
minimus. He holds the former view. A larva of Pelobates with 
six toes is regarded as settling this point. 
From this he turns to the existence of the prepollex in the Mamma- 
lia, and to Bardeleben's recent paper? on the foot of Pedetes. Similar 
bones to those described by Bardeleben as elements of the prepollex 
are known in other mammals, especially in the Rodentia. In other 
cases these structures are apparently ossifications of tendons. In the 
embryo of a rabbit Emery finds a true prepollex developed entirely 
independently of the fascia palmaris. This later migrates to the volar 
surface of the manus. This prepollex shows as many similarities with 
that of the Anura that Emery is not in doubt of their homology. 
Emery, however, regards the nail described by Bardeleben* on the 
prepollex of Pedetes as merely a horny growth. Bardeleben in turn® 
reaffirms his original statement, and quotes from a letter by Kohl- 
brugge, in which three specimens are mentioned with a true nail on 
this digit and a fourth with a horny cup. He also supports Bardele- 
ben in his view of two phalanges in the prepollex of Pedetes. 
1 Anat. Anz., V., 283. 
2 Proc. Zool. Socy. London, 1888. 
3 Proc. Zool. Socy. London, 1889. 
Le 
5 Anat. Anz., V., P- 32I, 1890. 
