Stockard, The Experimental Production of various Eye Abnormalities etc. 54 1 



trically monophthalmic. The fish were in better general condition 

 in the Mg Solutions than in other substances. Mg effects the deve- 

 lopment of the eyes without causing, in many cases, defects or 

 weaknesses in other parts of the central nervous System. Alcohol 

 on the other hand disturbs the development of the central ner- 

 vous system as a whole so that embryos are rarely strong after 

 treatment with it. 



These experiments prove that many of the eye malformations 

 met with in nature are probably due to some abnormal condition 

 in the developmental environment having acted upon the early 

 embryo. Anaesthesia tends to weaken or lower the dynamic pro- 

 cesses of development and it is probable that other causes which 

 would interfear with normal neutritian might cause similar effects. 

 This would apply especially to the mammalian egg where the 

 yolk has been lost and the embryo depends upon a perfect placen- 

 tation for its proper nourishment from the mother. I suggest, 

 therefore, that cyclopia and other Ophthalmie defects in mammals 

 are due to poor placentation or a diseased condition of the mother 

 which subjeets the embryo to an abnormal environment during 

 development. In man such defects are probably often due to an 

 alcoholic mother. There is no evidence to indicate that these 

 defects are the result of a peculiar or abnormal germ cell, and 

 against such a view the experimenter has the power to cause 

 at will perfectly normal eggs to develop into cyclopean monsters 

 by the use of alcohol and other anaesthetic agents. 



In a recent paper in the American Jour. of Anatomy, X, 

 p. 369, I have discussed the anatomical conditions of cyclopia and 

 shall not mention them here. 



Development of the Primary Parts 

 of the Eye. 



The embryos discussed above furnish excellent material for 

 a study of the relationship between the development of the optic 

 vesicle and the crystalline lens; the two primary parts of the 

 eye which arise in the embryo from different sources, the vesicle 

 from the brain wall and the lens from the head ectoderm. It 

 has been claimed by several experimenters that the optic-vesicle 

 was entirely independent of the lens in its development, while 

 on the other hand, the lens was entirely dependent upon the 

 optic vesicle for its origin from the ectoderm as well as for its 

 later differentiation into the clear refractive lens of the eye. 



A study of embryos having no optic vesicles, others with a 

 vesicle on only one side and finally those with a median cyclopean 

 eye show the following facts regarding the relationship between 

 the development of the optic vesicle and optic lens. 



The crystalline lens may originate from ectoderm without any 

 direct Stimulus whatever from an optic vesicle or cup. These self- 



VIII. Internationaler Zoologen- Kongreß. 41 



