. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 457 Squalus acantbias Petromyzon marinus. M. rectus posterior*) Degenerates Istpost-otic. Degenerates in early stages. 2nd post-otic. Degene- rates in late stages. 3nd post-otic. 1st perma- nent myotome. 4th — 8th post - otic [ myotomes give rise I by buds to hypo- \ glossus musculature I The 13th and following myotomes give rise by buds to the appendi- cular and ventral mus- culature (behind the procoracoid) M. rectus posterior Degenerates 1st post-otic Myo. 2nd „ „ 3rd „ ,, give rise by buds to the M. par. vent, bran- chial
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 457 Squalus acantbias Petromyzon marinus. M. rectus posterior*) Degenerates Istpost-otic. Degenerates in early stages. 2nd post-otic. Degene- rates in late stages. 3nd post-otic. 1st perma- nent myotome. 4th — 8th post - otic [ myotomes give rise I by buds to hypo- \ glossus musculature I The 13th and following myotomes give rise by buds to the appendi- cular and ventral mus- culature (behind the procoracoid) M. rectus posterior Degenerates 1st post-otic Myo. 2nd „ „ 3rd „ ,, give rise by buds to the M. par. vent, bran- chialis 8 4 th 9 5th 10 6th 11 *7th^ 12* *8th 13* *9th 14* *10th 15* *llthj 16 12 VII IX X 'Vagusanhang' 1st sp. 2nd „ 3rd „ 4th „ 5th „ 6th „ 7th ,, 8th „ VI None 1st to 5th post-otic myotomes innervated by the ventral roots of the 4th—5th post- otic myotomes ^) 3rd sp. 4th „ 5th „ 6 th 7 th 8 th 9th :^ "ramus re- currens vagi" of Kdpffer. par letalis ventralis lies three segments posterior to that (4th post-otic) wich in Squalus forms the anterior segment of the hypo- glossus musculature. We may draw from this the interesting con- clusion that in these two forms, buds from myotomes three segments removed come to lie in the same relative position anterior to the hyoid arch. The evidence that we possess shows, however, that this anterior segment does not enter into the formation of the muscles of the tongue ("piston lingual") of Petromyzon, as it does in Gnatho- stomata. Bujor ('91, p. 82) states that at metamorphosis "les muscles du piston lingual et ceux du pharynx naissent dans le tissu embryon- naire apparu apres la destruction du velum et de la glande thyroide". While I am not satisfied that the evidence given by Bujor has excluded the possibility that the M. par. ventralis contributes to the formation of the muscles of the "piston lingual", especially as he states in agreement with Schneider (79) that this muscl
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