MORPHOLOGICAL STUDIES. 
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think, very clearly that, contrary to Professor Froriep’s recent 
criticism (No. 19, p. 821), I was then fully aware of a point to 
which he attaches a very great deal of importance, viz. their 
typical position over a gill-cleft. The note is, “The nose is not 
a gill-slit but the sense organ which sits above a cleft.” 
In my paper on the branchial sense organs (No. 6) I showed 
that out of this epiblastic fusion, which (No. 5) I had described 
independently of Froriep, the sense organs of the lateral line 
or branchial sense organs take their origin. The sensory 
epithelium grows in various directions by division of its cells, 
and it pushes away the indifferent epiblast. From the sensory 
epithelium arise both sense organs and the nerves which supply 
them and connect them with the ganglia. The ganglia were 
considered as mainly arising from the thickenings, the cells 
derived from the neural ridge only forming the root of the 
nerve. Whether the latter conclusion is true or not I cannot 
say, certainly some of those cells do take part in the formation 
of the nerve, and their nuclei may be found along the course 
of the nerve. The suprabranchial nerves were distinguished 
from the praebranchial and postbranchial, and a morpho- 
logical importance was attached to the former. At the present 
time I regard the nature and mode of origin of suprabranchial, 
praebranchial, and postbranchial nerves, so far as the latter 
innervate the sense organs (for, as is well known, they also 
contain motor fibres to the muscles of the gill-cleft) as entirely 
the same, and would now say all the nerves to the sense organs 
of the lateral line or branchial sense organs are derived from 
the neuro-epithelial “ Aulagen ” of the latter. 
Nothing was said in my former paper of the origin of the 
neural-ridge of the spinal nerves, which lay beyond the scope of 
my researches at that time. Nose and ear were considered as 
modified branchial sense organs and their ganglia (for, in spite 
of Gegeubaur, the nose 1 has a ganglion) as differentiations of 
the sensory epithelium. Rudiments of such branchial sense 
organs and their ganglionic fusion were described in three- 
days’-Chick embryos. Spencer (No. 59) on Amphibia (Frog), 
1 Sec No. IV of these Studies. 
