Vol. XXXVIII. March, 1920. No. 3. 



BIOLOGICAL BULLETIN 



CARBON DIOXIDE PRODUCTION IN RELATION TO 



REGENERATION IN PLANARIA 



DOROTOCEPHALA. 1 



HARRIET L. ROBBINS AND C. M. CHILD. 



Numerous lines of evidence indicate that the body of Planaria 

 dorotocephala consists physiologically of more than one individual 

 or "zooid" after a certain limit of size is exceeded in the course 

 of growth. The first or chief zooid of the series includes the 

 region from the head to a level slightly posterior to the mouth, 

 the level at which fission usually occurs, and the region posterior 

 to this consists of one or more short zooids, the limits of which 

 can be distinguished physiologically, but not morphologically 

 (Child, '10, nc, '15, chap. VI). The susceptibility of the 

 body to a large number of chemical and physical agents in con- 

 centrations or intensities too high to permit acclimation or 

 tolerance, decreases from the head posteriorly through the 

 length of the first zooid, increases sharply at the level of fission 

 and in long animals shows one or more rises posterior to that 

 level (Child '13^). The process of regeneration also shows 

 graded differences at different levels, corresponding to the dif- 

 ferences in susceptibility (Child 'lib). 



In the papers referred to, as well as in many others evidence 

 has been presented to that the susceptibility differences in general 

 are in some degree an indicator of quantitative differences in 

 metabolic condition, particularly in rate of oxidations, though 

 susceptibility has never been regarded as an exact quantitative 

 measure of oxidation. According to this point of view the 

 gradations of susceptibility in the body of Planaria dorotoceph- 

 ala indicate that the rate of oxidation decreases gradually, at 



1 From the Hull Zoological Laboratory, University of Chicago. 



103 



