74 
& 
myotomes develops, those produced by the glossopharyngeus-- 
and vagus-somite differing externally in no way from 
next ones. The only indication of the beginning of the- 
process of reduction of the two anterior post-otic myotomes, 
which we see atrophy in higher Craniates, is the dís- 
appearance in the course of development of their deeper parts- 
(KOLTZOFF, 1902, p. 329). This 
fact evidently is accounted for 
by the circumstance that the 
roots of the anterior post-ctic 
myotomes also get lost, these 
myotomes being supplied by 
branches from the ventral m5 
roots of the 4t# and 5t® post-otic 
myotomes (cf. fig 20). 
Just as in Amphioxus there is 
a numerical, though not strictly 
aud:tory capsule by its increa- e 
zing size no longer finds suf- SA 
ficient room in one segment es Er 
but reaches (and the cranium 0 
with it!) into the first and Eee 
second post-otic segment, the 0 
corresponding _ myocommata m.- d) 
beir.g attached to it, as shown aA gj v 
by fig. 29, after GOODRICH m2 de) 
(1907, p. 40). According to î 
NEAL (1897, p. 446) the ventral m3 |) 
individual, correspondence be- 
tween the gill-slits and the 
somites (NEAL, 1897, p. 447, 
KOLTZOFF, 1902, p. 432), the 
eight gil! pouches, of which the 
first, the spiracular one, does 
not break through, being situa- 
ted originally between the first 
Fig. 28 Reconstruction írom ä 
series of horizontal sections 
through the head of Ammocoetes” 
at the time of hatching, after 
KLTZOFF, 1902, p. 556. 
au auditory vesicle, m.', m° etc. 
that of Amphioxus (the left-sided gill-slit between the first and 
second somite) but evidently to a pair of fuse 
d gill-slits in: 
front of the first or mandibular somite. 
