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EDWARD PHELPS ALLIS. 
of its own arch. Reference to Vetter’s figures then certainly 
shows that Dohrn intended to include the musculus inter- 
arcualis dorsalis I of Vetter’s descriptions in the muscles 
termed interarcuales by himself, for that muscle is the only 
one that extends from the pharyngobrancliial of one arch to 
that of the next posterior arch. Fiirbringer (1897), however, 
maintains that the interarcuales dorsales I were not intended 
by Dohrn to be so included. Fiirbringer had previously 
found (1895) that these musculi interarcuales dorsales I were 
innervated by spinal or spino-occipital nerves, instead of, as 
Vetter maintained, by branches of the related branch of the 
nervus vagus, and he (Fiirbringer) proposed for them the 
name musculi interbasales. In his later work Fiirbringer says 
(1897, p. 406), in making reference to Dohrn’s work: a Der 
Mm. interbasales thut er keine Erwahnung.” This is strictly 
correct, but Dohrn also does not specifically mention either 
the interarcuales II or III, and it is certain that if so careful 
a worker as Dohrn had intended to exclude either of these 
three muscles from the term interarcuales as employed by him 
he would have definitely said so. This is all the more evident 
from the fact that, without making reference to these musculi 
interarcuales I, Dohrn himself says, in the work in question 
(loc. cit., p. 117), that the musculus subspinalis of Vetter’s 
descriptions, which is simply an anterior member of the 
interarcuales dorsales 1 series (Allis, 1915), is probably derived 
from trunk myotones. 
Edgworth says (1911, p. 234) that, in 17 mm. embryos of 
Scyllium, the lower end of each of the branchial myotonies 
grows backward and becomes cut off from the remainder of 
the myotome to form the coracobranchialis. The ventral end 
of the remainder of the myotome is said to then grow ventrally, 
external to the Anlagen of the several coracobranchiales, to 
form the ventral end of the constrictor superficialis. It is 
then said that : “ The upper ends of the myotonies, in embryos 
between the lengths of 17 and 20 mm., increase in antero- 
posterior extent, and, fusing together, extend backwards as 
the trapezius to the shoulder-girdle. Below the Anlagen of 
