THE DEVELOPMENT OF ARTIFICIALLY PRODUCED 

 CYCLOPEAN FISH— "THE MAGNESIUM EMBRYO" 



BY 



CHARLES R. STOCKARD 



With One Plate and Sixty-three Text Figures 



Introduction 285 



Material and method 287 



Cyclocephali and Monstra Monophthalmica Asymmetrica 292 



a Living cyclopean monsters from the first indication of the defect to the time of hatching 294 



h Free swimming cyclopean fish 298 



c Living Monstra Monophthalmica Asymmetrica 304 



Morphology of Cyclocephalia 305 



a Earliest indication, exact position and condition of the eye 305 



b Incomplete cyclopia; double eyes 310 



c Perfect single cyclopean eye and normal brain 311 



d Extreme cyclopia; from the abnormally small anterior cyclopean eye to entire absence of 



eyes 315 



Incomplete diprosopus, with three eyes and one additional lens 322 



Morphology of Monstra Monophthalmica Asymmetrica 325 



Independent origin and self-differentiation of the crystalline lens 328 



Discussion and conclusions 330 



Summary 334 



Literature cited 336 



INTRODUCTION 



Development is the resultant of the interaction between the 

 inherent tendencies contained within the egg substance itself and 

 the external conditions which surround and act upon this sub- 

 stance. The usual interaction of these factors gives rise to 

 normal animal forms. When, however, either factor is changed 

 an unusual form results; in the one case there arises a germinal 

 variant, and in the other an anomaly occurs as a response to the 

 strange external environment. The product of development, the 

 formed animal, is then to a certain extent a creature of its environ- 

 ment. On the other hand the importance of the internal factors 

 must- be recognized although modern experimental work often- 



The Journal of Experimental Zoology, vol. vi, no. 2. 



