54 F, L. LANDACRE 
cessive branchial ganglia extend ventrally. In Squalus this 
mass of cells is replaced by the fibrous roots of IX and X and 
contains no cells except those of the jugular ganglion which are 
situated here up to the 25 mm. stage. 
The very small size of the r. oph. sup. V in comparison with 
the large r. oph. prof. is worthy of note. The disappearance 
of the profundus nerve in higher forms is certainly not fore- 
shadowed in Squalus. If we compare with these conditions the 
condition in Amphibia (Coghill, ’01, 02, ’06), where the oph- 
thalmic nerve is treated as an ophthalmicus profundus, it raises 
an interesting question concerning the relationship of these 
forms with the higher vertebrates which have apparently lost 
both the ophthalmicus profundus ganglion and nerve. How- 
ever, the ophthalmicus profundus ganglion is said to be present 
in the cat between the stages of 10 and 21 somites but its fate 
is not described (Shulte and Tilney, 15). 
The usual conception of the sharks as generalized verte- 
brates is borne out by the condition of the ganglia and nerves 
with the possible exception of the general cutaneous component. 
