359 
Nachdruck verboten. 
On the Development of the Vertebral Column in Pipa and 
Xenopus. 
By W. G. Rivewoop, B. Sc., F. L. S., Lecturer on Biology 
at St. Mary’s Hospital Medical School, London. 
With 4 Figures. 
While recently engaged upon an investigation on the mode of 
development of the hyobranchial skeleton of Xenopus and Pipa 
(the results of which are now appearing in the April number of the 
Journal of the Linnean Society, London), I chanced upon the interest- 
ing fact that free ribs are present in the young of both of these 
genera. The making of careful preparations of the vertebral column 
subsequently revealed other features of sufficient interest and import- 
ance to be worthy of publication, and the present paper is a record 
of the facts observed. The inquiry makes no pretence to completeness, 
and the accompanying descriptions apply only to such details as can 
be made out under the dissecting microscope. They do not include 
observations on those earliest stages of development the study of 
which involves histological treatment. In order to make certain that 
the first specimens examined were not abnormal, I dissected a large 
series of larve of Pipa and Xenopus of various stages of growth, 
and, with the further object of ascertaining how far the vertebral 
development of these genera departs from the normal Anuran types, 
I also made preparations of the vertebral column in larve of Rana 
esculenta, Rana temporaria, Bufo viridis, Alytes obste- 
tricans, Pelodytes punctatus and Pelobates fuscus. For 
nearly all of these specimens I am indebted to the gracious liberality of 
Mr. G. A. BOULENGER, F. R. S., of the Natural History Museum, London. 
Our knowledge of the development of the vertebral column in 
Anura generally we owe mainly to Duczs (12), MULLER (31), BRUCH (7), 
GEGENBAUR (16 and 17), Gorre (18), Scaweamann (38), Hasse (20) 
and Fietp (13). A methodical study of the embryonic vertebral 
column of Pipa has only been attempted by KoELLIKER (26) and 
GEGENBAUR (17, p. 34—41), although many investigators have exami- 
ned the embryos of Pipa to see if in early stages of growth the first 
two vertebre show any signs of distinctness. I have met with no 
references whatever to the vertebral column of the larval Xenopus. 
