FFB 24 1908 
The Ohio -Naturalist, 
PUBLISHED BY 
The Biological Club of ihe Ohio State University. 
Volume VIII. FEBRUARY, 1908. 
No. 4. 
TABLE OF CONTENTS 
I. andacre—T he Epi-branchial placodes of Ameiurus. 251 
Schai'fner—O n the Origin of Polar Conjugation in the Angiosperms . . 255 
Hix f.—S ome Observations C' neerniiig the Effects of Freezing on Insect Larvae.. 258 
Hammond—T he Embryology of Oxalis corniculata. 261 
Sterki—S ome Notes on Philomycus. . 265 
Hammond —McCray—M eetings of the Biological Club. 267 
J. C. H.—Book Review. 269 
LtBI 
NEW 
BOT/ 
GAfr 
THE EPI-BRANCHIAL PLACODES OF AMEIURUS.* 
F. L. Landacre. 
The study of the epi-branchial placodes of Ameiurus was 
taken up with the object of ascertaining to what extent they 
enter into the composition of the cranial nerves in this group 
of Teleosts. 
The catfishes with their enormously hypertrophied system of 
gustatory nerves ought to have these placodes correspondingly 
prominent during embryonic development if they are concerned 
in the origin of the communis portions of the cranial ganglia. 
Ameiurus has proven to be an unusually favorable type and 
a study of the development of its epi-branchial placodes suggests 
the idea that possibly the extremely divergent accounts given in 
the literature of these structures may be due to the choice of 
unfavorable types for study. 
The extent to which communis fibres enter into the composi¬ 
tion of the cranial nerves varies greatly even among the teleosts. 
There is probably a corresponding variation in the distinctness 
with which the placodes may be traced in the early development 
of those types in which the system is reduced. At any rate they 
are far more prominent and easily followed in Ameiurus than 
they seem to be in any other form described. 
Aside from working out the details of their origin the follow¬ 
ing queries have been kept more or less constantly in mind: 
(1) Do the cells derived wholly or in part from the placodes 
really become the communis ganglia of the adult? 
(2) Are the placodal portions of the cranial ganglia pure-^- 
i. e., are the communis ganglia derived exclusively from the 
* Read at the 1907 meeting of the Ohio Academy of Science. 
