534 



BERTRAM G. SMITH 



TABLE 1 



Metamorphosis: Two years after fertilization. 



a large yolk plug persists long after the closure of the neural 

 folds; such embryos usually produce normal larvae, though spina 

 bifida is an occasional result. In extreme cases the blastopore 

 may form entirely above the equator; such embryos die before 

 reaching the larval stage. 



This abnormality appears most frequently in eggs that have 

 been kept in jars of water during warm weather, and especially 

 in material that has been shipped long distances. Probably it 

 may be brought about by a variety of unfavorable conditions: 

 heat, lack of oxygen, mechanical agitation, and injurious sub- 

 stances (e.g., cinders) in the water. It is readily produced by 

 treatment with sodium chlorid ; very marked cases of spina bifida 

 may result. 



