538 BERTRAM G. SMITH 



merely the persistence of an embryonic condition; for in eai'ly 

 stages the tail is always strongly flexed and in these particular 

 cases it failed to straighten out. But as development progressed 

 the tail became twisted into a pronounced spiral. The illustra- 

 tions show the extreme condition; cases occur forming a series in- 

 termediate between this and the normal. In some cases the back 

 is arched or humped. So far as can be judged from surface views, 



J'ig. 201 Spiral-tailed moiistor of Cryptobranchus allegheniensis at the time 

 of hatching. Photographed from the living embryo anaesthetized with chlorc- 

 tone. X 3. 



the entire abnormality seems to ]3e brought about by the con- 

 stricting effect of a band of tissue lying in the ventral median line. 



As a result of this malformation, the larva is compelled to lie 

 on one side, and can swim only in a grotesque fashion, with back- 

 ward circling movements. Affected larvae take no food, and 

 die shortly after using up their supply of yolk. 



An analysis of the water was secured but the subject has not 

 yet been further investigated. Stockard ('()(), p. 119) noted 

 the occurrence of a similar abnormality in Fundulus embryos. 



