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myzon, there are three, as found by Miss PLATT (1897, 
p &50) in Necturus. To judge from MARCUS' (1910) figures 
and. descriptions this also holds good for Gymnophiones (the 
last, permanent, myotome of the head e.g. is situated here also 
above the space between the 4!t and the 5t® visceral cleft), 
although certain corrections of MARCUS'’ inter pretations seem 
necessary. In the axolotl (and the sturgeon) SEWERTZOFF 
(1895 p. 260) observed on y two post-otic somites in front 
of the occipital arch but, since in Selachians their number 
is also three, he leaves open the possibility that one has 
fallen out behind the auditory caosule. while Miss PLATT 
(1898, p. 450) suggests that SEWERTZOFF has made a mis- 
take. This has been fuliy confirmed by GOODRICH (1911, 
p. 116) who also comes to the conclusion that there 
are three pos!-otic segments included in the skull of 
Siredon. This number corresponds to that found in Pétromyzont 
between the auditory capsule and the first neural arch. 
Of the three post-otic head somites the anterior two, the 
glossopharyngeus and the primary vagus somite, no longer 
develop permanent muscles, they have been crushed out of 
existence, so to speak, by the auditory capsule. A little 
transient myotome, designated by him as y, is found by 
MARCUS (1910, p. 430) close to the vagus-ganglion and also a 
corresponding ventral root y. Afterwards, however, both break 
down while in Necturus, according to Miss PLATT (1898, 
p. 447), and in Siredon. according to GOODRICH (1911), à 
few fibres persist, continuous with the dorsal part of the- 
third post-otic somite. This somite, being the one of the 
“spinalartiger Vagusanhang’’, produces in Urodelans the 
anterior segment of the trunk musculature, attached, as 
recorded above, at the auditory capsule and inne:vated by 
the ventral occipital nerve (wrongly) designated as 2. 
Recently my friend VAN SETERS (1921) has come to the 
interesting conclusion, that in Anurans the skull is still 
one segment shorter than in Urodelans. Thus the first 
post- cranial segment would be the one corresponding to the 
“spinalartiger Vagusanhang.” This explains why in Anurans, 
where the myotome belonging to this segment, together 
with its ventral nerve-root, atrophies, not only the first 
(the “spinalartiger Vagusanhang’’) but also the second spinal 
ganelion, gets lost. 
e shall call the cranium of Urodelans a complete 
palaeo-cranium, comprising the rudiment of only one 
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