296 W. M. BALDWIN. 



was permitted to progress without further interference, the long 

 axis of the trunk of the embryos was invariably bent towards 

 one or the other side. The level of this bending or flexure of 

 the trunk depended directly upon the location of the area in- 

 fluenced by the light. 



Since the jelly which envelops the eggs had been found in 

 the spina bifida experiments to be impervious to ultra-violet 

 light rays, care was taken to remove it prior to the experiments- 

 As a result a marked increase in the percentage of positive results 

 followed the raying. Where, as was the case more particularly 

 with green frog's eggs, the jelly could be removed almost com- 

 pletely, about every egg rayed developed an abnormality which 

 conformed to this general, U-shaped type. Three type-exptri- 

 ments may be presented for the purpose of demonstrating the 

 constancy of results. On May 27, 1914, 9 eggs in the two-celled 

 stage were rayed, each for i minute. One died before develop- 

 ment had progressed more than 24 hours. Of the 8 remaining 

 all were U-shaped. Three of these were permitted to develop 

 until the tail and head were well'formed. The others were killed 

 at earlier developmental stages. On June 18, 1914, 25 eggs 

 were rayed, each for 30 seconds. These were in the one- and 

 two-celled stage. Various portions of the prescribed area above 

 the equator were influenced. Three died within 24 hours, one 

 lived until the neural groove had disappeared and presented a 

 marked curvature of the trunk. All of the remaining 21 were 

 U-shaped. On June 23, 1914, an exposure of 19 eggs in the one- 

 and two-celled ' stage was made, each for 30 seconds. Eight of 

 these were rayed in the designated area, and 1 1 along the equator. 

 One of the eight died early, of the remaining 7 all were U-shaped. 

 The 1 1 others demonstrated spina bifida. 



The inference seems justifiable, therefore, that the constant 

 type of defect produced is the result of a constant and uniform 

 degree of alteration of the superficially-placed egg substance in 

 the area illuminated. Just what the nature of this effect is we 

 are at present unable to state. It would appear that the proto- 

 plasm, using this term in its broadest sense, had been modified 

 in some chemical way to a degree which not only rendered it 

 unfit for participation in the subsequent chemical ontogenetic 



