134 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
is a characteristic of the higher autostylic fishes (Holo- 
cephalt and Dipnot); and if the above determinations are 
correct, it must be regarded as a tendency, most marked 
in that type of skull, which the Myxinoids have carried to 
its greatest pitch, with an accompanying degeneration of 
the Meckelian element. 
Both Furbinger and Parker agree in refusing to homo- 
logize the great lingual cartilage of the Lamprey (PI. IX, 
fig. 1, p.v.) with that much more extensive one in the Hags 
which, at first sight, it so fully resembles (fig. 2, a.v.). 
On comparing transverse sections across the heads of the 
Lamprey and Hag (Bdellostoma) the lngual cartilage of 
the former 1s seen to lie within the great muscular mass 
extending back towards the pericardium, while that referred 
to in the Hag occupies a superficial position ventrally. 
Moreover, not only is the latter free of the tongue, but 
that organ is supported by a delicate cartilage lying for 
the most part within the tendon of the central retractor 
muscle (‘‘longitudinalis lingue’’ of Furbinger), asymmet- 
rically displaced (fig. 4, p.v.) towards the right side. If, 
however, the sections be taken far enough forwards, it will 
be found that a small T shaped cartilage present in the 
Lamprey (a.v. figs. 1 and 3) (the “‘ median ventral”’ of 
Huxley) has the fundamental relationships of the domin- 
ant monster of the Hag; and, partly for this reason, partly 
for others given below (p. 187) I regard these as homolo- 
gous. On doing this, I can only look upon the slender 
chondrification lying within the tendon above named as 
the equivalent of the main support of the Lamprey’s 
tongue; and reflection leads me to the conclusion that 
the median ventral cartilages of the two types are reducible 
to the same plan, but inversely modified in the one animal 
as compared with the other. If, as can hardly be doubted, 
the ‘‘tongue”’ of the Marsipobranchii is an organ peculiar 
