ORIGIN OF MONSTERS 529 



Of quite particular interest in connection with my own results 

 reported in this paper are Child's ('15 b) experiments on starfish 

 eggs. If these were subjected at early stages of development to 

 the influence of solutions of potassium cj'-anide not strong enough 

 to kill the eggs, the resulting larvae exhibited the detrimental 

 effect of the sojourn in the toxic solution mainly in the apical 

 region.^ Here, as well as in my experiments on Fundulus the 

 part of the egg destroyed by chemical action is the one which 

 corresponds potentially to the embryo's apical (animal) pole. 



Very recently Child ('15 a) has concluded that this primary 

 gradient from the 'animal pole' to the 'vegetative pole' is very 

 general in organic life and that its demonstraton is only difficult 

 in higher animals, where, owing to complex organization, the 

 results of the 'resistance method,' by which they can be demon- 

 strated in invertebrates, are obscured. 



In the early embryo, however, before the differentiation of or- 

 gans, when the physiological conditions are yet relatively simple, 

 the assumption of such an 'axial gradient' in the susceptibility 

 of the fish egg would seem to be justified. 



If, however, this gradient of metabolic reactions exists in the 

 fish egg, then there exists also a point' of highest susceptibility 

 and accordingly of least resistance; and this point (the animal 

 pole) is the potential anterior end of the embryo's body. Grant- 

 ing this, however, it is no longer difficult to understand why 

 the effect of the toxic solution on Fundulus eggs should, as it so 

 often does, manifest itself in defects of organs of the anterior end 

 of the body, and most particularly the eyes, the mouth, the 

 olfactory pits, and the forebrain, while the rest of the body may 

 suffer very little from the sojourn in the solution. 



Many observations point to the conclusion that this injury at 

 the apical pole which results in terata of the eyes, is caused 

 mainly by a process of disintegration and dissociation which I 

 have termed blastolysis. It is not easy to understand just what 



" Very recently Painter ('15) observed that in Ascaris eggs which have by an 

 accident come under the influence of carbon dioxide "roughly 33 per cent of the 

 embryos (in 54 cases out of 165 examined for the point)" have sustained severe 

 injuries at the anterior end. 



