AUTHOR S ABSTRACT OF THIS PAPER ISSUED BY 

 THE BIBLIOGRAPHIC SERVICE, SEPTEMBER 28. 



METABOLIC GRADIENTS IN AMOEBA AND THEIR 

 RELATION TO THE MECHANISM OF AMOEBOID 

 MOVEMENT 



LIBBIE H. HYMAN 



Hull Zoological Laboratory, University of Chicago 



FOURTEEN FIGURES 



I. INTRODUCTORY REMARKS 



The existence of a differential axial susceptibility to certain 

 substances has now been demonstrated for a number of adult 

 and embryonic organisms, including algae, representatives of 

 most of the groups of lower invertebrates, and embryos of echino- 

 derms, annelids, and vertebrates. 1 This work has shown that the 

 anterior end, head, or apical region of these organisms is most 

 susceptible to lethal concentrations of the substances in ques- 

 tion and that this susceptibility decreases along the principal 

 axis of symmetry. In some cases it has been possible to demon- 

 strate differential susceptibility along other axes also, as the 

 ventro-dorsal axis, (dorso-ventral in vertebrates) and the medio- 

 lateral axis (Child, '15, Chap. III). 2 These gradients are the 

 cause of the formation of anterior or apical ends, and of axes of 

 symmetry and not the result of them. This phase of the mat- 

 ter cannot be discussed here but is treated to some extent in 

 Child ('15). 



1 A general discussion of metabolic gradients will- be found in Child ('15, 

 Chap. Ill), with references to papers published up to that time; since then, 

 the following papers on gradients have appeared: Hyman ('16 a), Child ('16 a, 

 '16 b, '16 d, '17 a, '17 b). 



2 Methylene blue has proved to be a particularly favorable reagent for the 

 demonstration of these minor axes. Thus in oligochaetes, killed in methylene 

 blue, it can plainly be seen that the disintegration proceeds faster along the 

 ventral side than along the dorsal side, and further that disintegration first 

 occurs in the ganglia of the ventral cord, indicating that the gradient has its 

 chief seat in the nervous system. 



55 



