i8o 
Journal of Agricultural Research 
Vol. XXVI, No 4. 
A litter mate of an otocephalus is not appreciably more likely to suffer 
the defect than a nonlitter mate. 
It is concluded that the condition of the dam and external factors which 
act alike on litter mates through their effect on the dam play a part in 
determining otocephaly, but only a small part. 
By elimination it is concluded that the main factor is probably chance 
delay or other irregularity in implantation acting on a genetic basis of 
susceptibility at a particular, critical moment in ontogeny to the resulting 
temporary arrest in development. 
The grades of defect can be interpreted in harmony with Child’s gradient 
theory. 
The possibility is pointed out that many if not all genetic factors may 
have a simple accelerating or inhibitory effect on metabolism, as general 
in nature as those which seem to form the genetic basis of otocephaly, and 
that their control of the developmental pattern may rest merely on the 
order in which they come into activity as determined by conditions due 
to genes which have already acted. 
LITERATURE CITED 
(1) Child, Charles Manning. 
1921. THE ORIGIN AND DEVELOPMENT OP THE NERVOUS SYSTEM. XVii, 296 p., 
70 fig. Chicago. References, p. 273-288. 
(2) Dareste, Camille. 
1891. RECHERCHES SUR LA PRODUCTION ARTIFICIELLE DES MONSTRUOSIT^S. 
Ed. 2, xvi, 590 p., 62 fig., 16 pi. Paris. 
(3) Lewis, W. H. 
1909. THE EXPERIMENTAL PRODUCTION OF CYCLOPIA IN THE FISH EMBRYO, 
(fundulus heteroclitus). In Anat. Rec., v. 3, p. 175-181, illus. 
(4) Mall, Franklin P. 
1908. A STUDY OF THE CAUSES UNDERLYING THE ORIGIN OF HUMAN MONSTERS. 
In Jour. Morph., v. 19, p. 1-361, illus., 4 pi. 
(s)- 
1917. ON THE FREQUENCY OF LOCALIZED ANOMALIES IN HUMAN EMBRYOS AND 
Infants at birth. In Amer. Jour. Anat., v. 22, p. 49-72, 18 fig. 
(6) Platt, Julia B. 
1898. THE DEVELOPMENT OF THE CARTILAGINOUS SKULL AND OF THE BRANCHIAL 
and hypoglossal musculature in nEcturus. In Morph. Jahrb., 
Bd 25, p. 3 77-464, pi. 16-18. Literature cited, p. 459-462. 
(7) Saint-Hilaire, Isidore Geoffroy. 
1832-37. HISTOIRE G^N^RALE ET PARTICULI^RE DES ANOMALIES DE L’ORGAN¬ 
ISATION CHEZ L’HOMME ET LES ANIMAUX. 3 V. BrUXelleS. 
(8) Stockard, Charles R. 
1909. THE ARTIFICIAL PRODUCTION OF ONE-EYED MONSTERS AND OTHER DEFECTS, 
which occur in nature, by the use of chemicals. In Anat. Rec., 
v. 3, p. 167-173, 5 fig. 
(9) —— 
1921. DEVELOPMENTAL RATE AND STRUCTURAL EXPRESSION: AN EXPERIMENTAL 
STUDY OF TWINS, “DOUBLE MONSTERS” AND SINGLE DEFORMITIES, 
AND THE INTERACTION AMONG EMBRYONIC ORGANS DURING THEIR 
origin and development. In Amer. Jour. Anat., v. 28, p. 115-277, 
32 fig., 6 pi. Literature cited, p. 263-266. 
(10) Stone, L. S. 
1922. EXPERIMENTS ON THE DEVELOPMENT OF THE CRANIAL GANGLIA AND THE 
LATERAL LINE SENSE ORGANS IN AMBLYSTOMA PUNCTATUM. In Jour. 
Exp. Zool., v. 35, p. 421-496, 90 fig. Literature cited, p. 495-496. 
(11) Werber, E. I. 
1915. EXPERIMENTAL STUDIES AIMING AT THE CONTROL OF DEFECTIVE AND 
monstrous development. In Anat. Rec., v. 9, p. 529-562, 29 fig. 
Literature cited, p. 561-562. 
