METABOLIC GRADIENTS OF VERTEBRATE EMBRYOS. 57 



Fundulus eggs. He used potassium chloride, lithium nitrate and 

 sulphate, calcium chloride, ammonium chloride, and magnesium 

 chloride, alone or in combinations. In solutions of all of these 

 substances embryos were obtained with poorly developed heads 

 and eyes, or with no eyes, with abnormal hearts and defective cir- 

 culatory systems, with shortened bodies, and open blastopores. In 

 magnesium chloride in particular, fifty per cent, of embryos with 

 various eye defects were obtained. All degrees of approximation 

 of the eyes were noted, to the cyclopean condition. Many one- 

 eyed monsters were obtained, in which one eye was small or 

 defective or wanting. Associated with the approximation of the 

 eyes was often an abnormality of the anterior part of the head 

 resulting in displacement and elongation of the mouth which pro- 

 jected ventrally like a proboscis. The forebrain in these embryos 

 with abnormal eyes may be nearly normal or reduced ; it is always 

 reduced when the cyclopean eye is reduced and defective. In 

 the extreme cases, the olfactory pits were fused also. Later 

 Stockard found that similar conditions could be produced by 

 anaesthetics, except that the eye defects were then accompanied 

 by other defects while with magnesium chloride it is possible to 

 produce defective eyes in embryos otherwise nearly normal. The 

 embryos produced in anaesthetics in addition to defective eyes 

 nearly always have narrow and defective brains, abnormal ear 

 vesicles, and defective posterior ends in the form of spina bifida. 

 Other investigators have obtained similar results. McQendon 

 ('i2a and b) obtained cylclopic Fundulus embryos by means of a 

 number of salts, anaesthetics and alkaloids. He states that in 

 nature cyclopic trout embryos arise in water containing an in- 

 sufficient quantity of oxygen and that he has observed cyclopean 

 smelt embryos which were possibly caused by an excessive car- 

 bon-dioxide content. Gee ('16) obtained abnormal Fund id us 

 embryos similar to those of Stockard by alcohol and sodium 

 hydroxide. These embryos were characterized by defective 

 heads and eyes, asymmetrical eyes, absence of eyes, shortened 

 bodies, defective circulation, and spina bifida. Gee found that 

 the defects are obtained if the egg is exposed to the solutions 

 before fertilization or shortly after fertilization. Kellicott ('16) 



