FACTORS WHICH DETERMINE OTOCEPHALY IN 
GUINEA PIGS 1 
By Sewall Wright, Senior Animal Husbandman in Animal Genetics , and Orson 
N. Eaton, Scientific Assistant in Animal Genetics, Animal Husbandry Division , 
United States Department of Agriculture 
INTRODUCTION 
Nearly all of the recognized types of monstrosities have appeared in the 
stock of guinea pigs maintained by the Bureau of Animal Industry for 
genetic experimentation. The most abundant type, unless all those 
with leg or toe abnormalities are lumped together, has been that which 
Pig. i. —Grades of otocephaly. Semidiagrammatic ventral views of the head and throat of the 12 grades 
in comparison with the normal (o). 
Geoffroy Saint-Hilaire (7) 2 called “ otoceph alien ” in his classical mono¬ 
graph on the subject. Certain of the grades are of the well-known 
cyclopean type. 
The most characteristic feature of these monsters is the close approach 
of the ears, there being in most cases but a single median opening in the 
throat. There has been wide variation in the degree of defect, but all 
the cases observed in our stock of guinea pigs fall practically into a single 
1 Accepted for publication Aug. 3, 1923. 
* Reference is made by number (italic) to “Literature cited,” p. 180-181. 
Journal of Agricultural Research, 
Washington, D. C. 
ohb 
(161) 
Vol. XXVI, No. 4 
Oct. 27, 1923 
Key No. A—64 
