361 
and, more recently, by AnoLput (1, p. 315) and Prrer (34, p. 571). 
But FÜRBRINGER (14, p. 179—180) gives it as his opinion that the 
first two components of the vertebral column of Pipa represent the 
first two of other Anura; in which case the sacral vertebra of Pipa 
is the eighth and in other Anura the ninth vertebra. And v. JHERING 
(25, p. 297) maintains that the first apparent vertebra of Pipa is 
the first of other Anura, that the second is equivalent to the third 
of other Anura, and that the second vertebra of the latter has been 
excalated in Pipa (25, p. 306). 
But the fact of the first spinal nerve of Pipa passing out through 
the wall of the neural arch is much more intelligible on the assumption 
that the aperture represents the intervertebral foramen between vertebree 
1 and 2 than on v. JHERING’s hypothesis, and the occurrence of di- 
apophyses in connection with the neural arch is a serious bar to the 
acceptance of the excalation theory, for in no anurous Amphibian are 
diapophyses known to occur on the first vertebra, either normally or 
abnormally. All cases in which the exceptional occurrence of diapo- 
physes on the first vertebra are recorded prove on inspection to be 
cases of confluence of the first true vertebra with the second, to which 
latter the diapophyses properly belong. The only cases which might 
be considered as exceptions to this statement are those described by 
Bourne (6) and Howes (24). Those of the latter author, however, 
are regarded by Aporpnı (2, p. 486) as examples of united first and 
second vertebree, and the same arguments will apply to BournE’s 
case of Rana temporaria. 
StAannıus (40, p. 15—16), FÜRBRINGER (14, p. 180), v. JHERING 
(25, p. 298), Apouput (1, p. 315), GRÖNBERG (19, p. 641) and PETER 
(34, p. 571) have examined the anterior end of the vertebral column 
of Pipa embryos with a view to discovering traces of the early in- 
dependence of the first and second vertebr®, but all have arrived at 
negative results. The most recent observations are those of PETER, 
who states that the first element of the vertebral column of Pipa is 
‚ undoubtedly the first and second vertebre combined, and remarks 
that the fusion must occur very early, for he has not been able to 
distinguish the two vertebre in a 1,5 cm long embryo. I have 
examined embryos very much younger than this and I consider it 
very doubtful if the vertebree are ever distinct. There are, I take 
it, in this first vertebral segment two potential vertebrae, but the 
chondrification of the skeletogenous tissue is single from the very first. 
Because in ontogeny we cannot distinguish the two phylogenetic entities, 
we are not in consequence to be debarred from considering that in 
this first segment of the spine are represented two undifferentiated 
Anat, Anz. XIII. Aufsiitze. 24. 
