AUTHOR'S ABSTRACT OF THIS PAPKR ISSUED 

 BY THE BIBLIOaKAPHIC SEIlv'ICE, MAY 1 



THE CONTROL OF HEAD FORMATION IN PLANARIA 

 BY MEANS OF ANESTHETICS 



J. WILLIAM BUCHANAN 



Hull Zoological Laboratory, University of Chicago 



THREE FIGURES 



Regeneration in Planaria has attracted the attention of in- 

 vestigators for more than a century, at least since 1791 (Ran- 

 dolph, '95). Record of mass experiments is absent from the 

 literature, however, until the closing years of the nineteenth 

 century (Morgan, '98). The present paper presents the results 

 of an attempt to analyze with the aid of certain narcotics the 

 conditions controlling the completeness of regeneration, par- 

 ticularly as regards the head, in pieces of Planaria. The data 

 consist of mass experiments which have involved the cutting of 

 more than forty thousand worms and the handhng of more than 

 one hundred and twenty thousand pieces. 



THE PROBLEM 



Cross-sections from the body of Planaria do not always 

 reconstitute new individuals with anterior ends like those in 

 nature. Abnormalities have been frequently produced experi- 

 mentally and described in many species and their occurrence 

 explained by diverse theories. In Planaria dorotocephala Child 

 ('11 a) has for convenience distinguished five classes of anterior 

 ends in regenerated pieces, each class continuous into the next. 

 Figure 1 shows the external appearance of the five types: nor- 

 mal (A), in which the head is the usual form of those in nature; 

 teratophthalmic {B, C, D), in which the shape of the head is 

 normal, but the eyes show some degree of abnormality ranging » 

 from shght reductions in size and approximation to the median 

 line, to a single median eye; teratomorphic (E), in which the 

 shape of the head is abnormal, reduced in size, and the cephalic 



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