530 E. I. WERBER 



chemical reactions may underlie this process. They obviously 

 depend entirely on the chemical nature of the solution employed. 

 Thus it would seem reasonable to expect that for instance they 

 are quite different in butyric acid solutions from those of mag- 

 nesium chloride solutions employed by Stockard ('09) or alkaloid 

 solutions employed by McClendon ('12 b). The action of some 

 solutions may dissolve, while that of other solutions may coagu- 

 late or precipitate Certain substances of the egg. However, no 

 matter what this action may be, it certainly results in a chemical 

 alteration, which will be the more intense, the higher the con- 

 centration of the solution or the longer the time of exposure. 

 Accordingly, if the action be a slight or moderate one, the chemi- 

 cal alteration may result only in an inhibition of certain groups 

 of cells possessing a high degree of susceptibility, i.e. these cells 

 may continue dividing and differentiating up to a certain point, 

 beyond which, owing to exhaustion of their chemical capacity, 

 they are unable to proceed. Or the action may be strong enough 

 to cause, by chemical alteration, a check of the most important 

 physiological processes (cell metabohsm and cell division) of 

 these embryonic cells, which would result in their disintegration. 

 No matter what chemical solution be employed, if it only is 

 injurious to life, it will in this way, have a destructive effect. 

 If non-lethal concentrations and lengths of exposure be em- 

 ployed, this destructive process will largely be restricted to the 

 animal pole of the egg, i.e., to that part of the egg which in 

 normal development would correspond to a certain area at the 

 anterior end of the potential embryo's body. Since, according 

 to the rule of the 'axial gradient' this destructive process — 

 chemical blastolysis — begins at the animal pole of the egg and 

 cannot proceed further, owing to insufficient strength of the 

 solution or to timely transfer to a normal environment (pure 

 sea-water), its effect is eventually noted in deformities at the 

 embryo's anterior end of the body. 



According to what has been said so far the sequence of events 

 leading to the deformities of the eye is, then, more or less the 

 following. 



