640 Dritte Sitzung der fünften und zehnten Sektion. 



fectly normal eye in its usual position on either the right or left 

 side of the head, while the eye of the other side may be either 

 smaller than usual, or very small and defective in structure, or 

 deeply buried in the head tissues as a choroid vesicle entirely 

 failing to form a typical eye, or finally, the optic vesicle of one 

 side may not arrise from the brain and thus the individual has 

 a perfect eye on one side and no indication of an eye on the other. 

 I have called such monsters as these "Monstrum Monophthalmi- 

 cum Asymmetricum" as distinguished from the cyclopean monster 

 with its one symmetrically placed eye. 



This type of monster seems rarer in nature than the well 

 known cyclops, altough they do occur. I have known a child 

 with one perfect eye and the other small and defective, and Pro- 

 fessor T. H. Morgan has shown me a pigeon that presented 

 a similar condition. 



The asymmetrical monophthalmic monsters are possibly due 

 to the different degrees of resistance to the anaesthetics possessed 

 by the anlagen of the two optic vesicles. The doses used are of 

 course very delicately adjusted. One eye begins to push out from 

 the brain slightly before the other (in studying normal embryos 

 it is often found that one organ of a bilateral pair forms and deve- 

 lops ahead of the other for a time) the weaker or slower eye is 

 affected by the Solutions while the stronger is not. The different 

 degrees of abnormality shown by one eye may be an index to the 

 more or less wide difference in developmental energy possessed 

 by the two eyes of the same individual. 



It is of interest to record here that in some cases the develop- 

 ment of the auditory vesicle or ear is affected by the alcoholic 

 Solutions. At times one ear is injured and the other not, in such 

 individuals when the eyes also exhibit an asymmetrical condition 

 it invariably happens that the defective eye is on the side with 

 the defective ear. The rates or strengths of development of the 

 sides of the embryo are different, in other words development 

 is not perfectly bilateral, one side may go ahead of the other 

 for a time then the other catches up and may actually get ahead 

 and so on. 



Still other cases occurred in which both eyes were small and 

 defective although they pushed out from the brain and reached 

 the sides of the head. The two eyes of these individuals show 

 the various degrees of imperfection found in the small eye of the 

 asymmetrical monophthalmic monsters. 



Alcohol was most effective of all the anaesthetics employed 

 in producing these conditions. Proper strength Solutions of alcohol 

 may cause as many as 98 per cent of the eggs to develop into 

 young fish exhibiting the various Ophthalmie defects mentioned 

 above. Magnesium salts in Solution were next in efficiency, in one 

 experiment 66 per cent of the embryos were cyclopean or asymme- 



