278 CHARLES R. STOCKARD 



of a type which would suggest lack of developmental energy 

 necessary to attain the normal. 



Another group of eye anomalies were extremely common under 

 the same experimental conditions which caused the cyclopean 

 series. These individuals possessed one normal eye in the usual 

 lateral position while the eye of the opposite side in the numer- 

 ous specimens showed various degrees of imperfection from a 

 condition slightly below the normal in size to complete absence 

 of the eye. Such anomalies were termed 'monophthalmica asym- 

 metrica' in contrast to the symmetrical one-eyed monsters with 

 a median cyclopean eye.i 



The genesis of the asymmetrical defects is not entirely clear, 

 yet they also are probably due to developmental arrest or sup- 

 pression of the one eye. The growth centers representing the 

 two future eyes of an individual are rarely equally vigorous and 

 it is frequently noticed that one eye arises slightly before its 

 mate and develops at a little faster rate. It might be that at 

 some critical point in development one of the future eye centers 

 is affected after the growth centers had begun to localize in more 

 or less lateral positions. 



In treating the eggs with alcohol a number of embryos occurred 

 in which both eyes were small and defective even though they 

 arose from the brain and attained more or less lateral positions. 

 One might assume this to occur as a result of an arrest in devel- 

 opment which affected both eye forming centers after the centers 

 became separate or distinct from one another. Part of the eye 

 forming material is suppressed or its differentiation is prevented 

 so that each eye is decidedly under size and defective. In some 

 of the cases of cyclopia mentioned above the eye was also very 

 small and defective, in these cases the two growth centers which 

 would give rise to the future lateral eyes did not become suffi- 

 ciently separated so that only a single median eye arose and 

 the reduced vigor permitted this to form only as a small and 

 poorly differentiated structure. 



In some instances where an embryo possessed only one mem- 

 ber of the normal eye pair this eye was unable to attain its usual 



