46 . 
Spiracula enthält”. I have also been unable to find myotomic buds 
from those myotomes (1th—6th post-otic) which primitively lie above 
the branchial basket. Moreover, since such growth could take place 
through the visceral arches only, and since muscle buds are insepar- 
ably connected with their nerves, we should expect, had such growth 
occurred, to find ventral spinal nerves passing to the M. par. sub- 
branchialis through the visceral arches. This I do not find to be 
the case. The ventral roots of the 4th and 5th myotomes innervate 
the anterior five myotomes, which have no ventral portion. The 
fibres of the ventral root of the 6th myotome extend posteriorly above 
the epibranchial portion of the vagus and may possibly innervate 
ventral musculature, but I hold this to be improbable since I do not 
find that this myotome develops a myotomic bud. The ventral roots 
of the 7th and following myotomes may, however, be traced ventrally 
behind the last visceral pouch to the M. par. ventralis. I con- 
sequently see no escape from the conclusion that the branchial portion 
of the M. par. ventralis, assuming that it is of myotomic origin, is a 
derivative of post-branchial myotomes only. The question whether the 
“Vag Anhang. 
re. sp.vertt N lat. r.cut.dors. i ‚gu vag. ‚gn.fac 
gls: gnteg” 1my. 
Fig. 2. Hypoglossus nerve and musculature as seen in an embryo of Pet. Planeri, 
of 5 cm. Z2—& Segments of the muse. parietalis subbranchialis; hyp. hypo- 
glossus nerve; my /— 14 post-otie myotomes 1— 14; m. ret. p. M. rectus posterior (externus); 
r. eut. dors. ramus cutaneus dorsalis; ra. sp. vent. ventral spinal nerve root; gn. sp.! first 
dorsal ganglion. 
number of segments in the M. par. subbranchialis corresponds 
with the number of myotomic buds which enter into its formation, 
must, I believe, be answered in the negative from the following 
evidence. 
