AUTHOR'S ABSTRACT OF THIS PAPER ISSUED BY 

 THE BIBLIOGRAPHIC SERVICE, DECEMBER 1 



DIFFERENTIAL SUSCEPTIBILITY AND DIFFEREN- 

 TIAL INHIBITION IN THE DEVELOPMENT OF 

 POLYCHETE ANNELIDS 



C. M. CHILD 



Hull Zoological Laboratory, University of Chicago, III. 



FIFTY-SEVEN FIGURES 



The existence of gradients in susceptibility to various agents 

 has been demonstrated for the eggs and developmental stages of 

 starfish and sea-urchin (Child, '15 c, '16 a), and the control and 

 modification of development through differential susceptibility 

 in the sea urchin (Child, '16 c) has shown the fundamental 

 significance for the development of this form of the axial gradients 

 in metabolic activity and protoplasmic condition of which the 

 susceptibility gradients are indicators. In the light of the results 

 obtained with echinoderms, the desirability of extending investi- 

 gations along these 'lines to other forms is evident. Since the 

 polychete differs so widely from the echinoderm in its highly 

 determinate cleavage, its very early larval differentiation and its 

 apparently limited regulatory capacity in early developmental 

 stages, the investigation of its development by means of the 

 susceptibility methods is of particular interest, not only for the 

 purpose of comparison of the two sharply contrasting forms, 

 but as a further contribution to the general theory of organiza- 

 tion. Such an investigation must determine as far as possible, 

 first, whether axial gradients are present or not, second, what 

 modifications they undergo during development and third, their 

 role in development. The data presented below, the result of 

 work done during the last four summers at the Marine Biological 

 Laboratory, Woods Hole, Mass., throw some light on these 

 problems. 



The differential susceptibility along an axis may appear in 

 sufficiently high concentrations of the agent employed as a 



1 



JOURNAL OF MORPHOLOGr, VOL. 30, NO. 1 

 DECEMBER, 1917 



